- Limit the effect of `nav_exclude: true` to the main navigation.
- Include links to excluded pages in auto-generating lists of child pages
and in breadcrumbs.
- Refactor implementation by moving assignment of `first_level_url` and `second_level_url` from `_includes/nav.html` to `_layouts/default.html`.
- Clarify the effect of `nav_exclude` in the documentation.

Correction needed for use of collections.

Co-authored-by: Kevin Lin <kevinl@cs.uw.edu>

Fixed conversion of numeric titles to strings.

Indentation adjusted

The values of `title` and `nav_order` can be numbers or strings.
Jekyll gives build failures when sorting on mixtures of different types,
so numbers and strings need to be sorted separately.

Here, numbers are sorted by their values, and come before all strings.
An omitted `nav_order` value is equivalent to the page's `title` value
(except that a numerical `title` value is treated as a string).

The case-sensitivity of string sorting is determined by `site.nav_sort`.

Pages with `nav_exclude: true` were included when sorting on `title` or `nav_order`. That could cause build failures when the type of value of the field differs from that on other pages, as reported in https://github.com/pmarsceill/just-the-docs/issues/406.

Pages with `nav_exclude: true` or no `title` are never displayed in the navigation, so removing them from `pages_list` cannot break existing sites. This change also allows the removal of some tests in the code. (The indentation of the code should now be adjusted, but that has been deferred, to restrict the size of the diff for review.)

For testing, the title of `404.html` has been changed to the number `404`,  the page `docs/untitled-test.md`  has been added, and `nav_sort_order` has been set to `case_sensitive`. Those updates give build failures with the current version of `_includes/nav.html`, but not after the suggested changes.

It will still be possible for build failures to occur due to sorting fields of *non-excluded* pages with differing types of values (e.g., `nav_order`a mixture of numbers and strings). To make the code completely safe will require relatively complicated changes,.

This improves Google Lighthouse accessibility score. As a human I agree that it was too faint.

Fixes a bug where content after headings in header elements disappeared.
Header elements are not currently used in JtD, but could make the HTML more semantic.

Now using an include parameter.
Enhanced to support Markdown with code fences.

I ran Lighthouse on just-the-docs and noticed the anchor links
were missing a "discernible name".

This adds aria-labelledby to the header element to improve these for
screenreaders.

The added examples in `docs/index-test.md` extend the previous examplees of highlighting, documenting the required inout.

Changed `site.html_pages` to `pages_list`, to repeat the nav order of the grandchildren in the nav panel.

Co-Authored-By: Patrick Marsceill <pmarsceill@users.noreply.github.com>

Added a configuration option to determine whether the sort order is case-sensitive.
The default is case-insensitive.

To test:
- open `/just-the-docs/docs/utilities/` in the browser,
  and check that the navigation links in `Utilities` are sorted alphabetically;
- in `docs/utilities/layout.md', change the preamble to `title: layout`,
  and check that the  links in `Utilities` are still sorted alphabetically;
- add `nav_sort: case_sensitive` in the configuration file,
  and check that the link to `layout` is now listed last under `Utilities`.

Co-Authored-By: Patrick Marsceill <pmarsceill@users.noreply.github.com>

Currently just-the-docs renders two title and description tags
when used with jekyll-seo-tag. This patch fixes plugin detection
conditonal.

It appears nav_exclude only works on top level navigation items. I needed it to work at the child level as well. I believe these changes accomplish that for the child and grand_child levels.

Love this theme. I've used it a few times. Apologies if this pull request is not according to convention. This is the first time I've done it on someone else's code. Thanks!

Display of grandchildren links in the navigation is now delayed until their parent is selected.

To test, select the `Grandchildren test` node. Only the direct children should appear. Selecting one of them then shows its children.

- Introduced "ga_tracking_anonymize_ip" parameter to enable/disable Google Analytics IP anonymization (to comply with GDPR).

(cherry picked from commit ce530f36fa0549c78ffe53ea6077f44f6f0b330f) (+1 squashed commit)
Squashed commits:
[69b7718] - enable GA anonymize_ip

(cherry picked from commit f2b67c632af72b61dd634b9a337200781519691e)

This commit resolves #207.

When `nav_order` is omitted, the order of nodes at each menu level (and in the auto-generated TOC) is alphabetical by `title`, instead of random.
Any nodes with a specified `nav_order` precede all nodes at that level where it is omitted.
Note that `nav_order` fields must have a uniform site-ide type: integers and strings cannot be mixed, otherwise Jekyll reports errors.
The implementation filters the ordered and unordered pages from `site.html_pages`, sorts them separately, and concatenates the resulting arrays.

This reverts commit 7220197a.

Mathjax config options added.
`compress_html` config option changed,
Mathjax script loaded by head when `page.mathjax` is truthy.
Documentation and test page added.
See also issue #198.

This reverts commit 0cfc0f03.

This reverts commit 8ac545a5.

This reverts commit c282e4b0.

This reverts commit 5d58a663.

This reverts commit 89f79138.

This reverts commit 209ac7be.

Restrict navigation to display only direct children.

This reverts commit 8ac545a5.