[Security] Bump mixin-deep from 1.3.1 to 1.3.2

Bumps [mixin-deep](https://github.com/jonschlinkert/mixin-deep) from 1.3.1 to 1.3.2. **This update includes a security fix.**
- [Release notes](https://github.com/jonschlinkert/mixin-deep/releases)
- [Commits](https://github.com/jonschlinkert/mixin-deep/compare/1.3.1...1.3.2

)

Signed-off-by: dependabot-preview[bot] <support@dependabot.com>

package-lock.json

 {
   "name": "just-the-docs",
-  "version": "0.2.5",
+  "version": "0.2.6",
   "lockfileVersion": 1,
   "requires": true,
   "dependencies": {
@@ -2776,9 +2776,9 @@
       }
     },
     "mixin-deep": {
-      "version": "1.3.1",
-      "resolved": "https://registry.npmjs.org/mixin-deep/-/mixin-deep-1.3.1.tgz",
-      "integrity": "sha512-8ZItLHeEgaqEvd5lYBXfm4EZSFCX29Jb9K+lAHhDKzReKBQKj3R+7NOF6tjqYi9t4oI8VUfaWITJQm86wnXGNQ==",
+      "version": "1.3.2",
+      "resolved": "https://registry.npmjs.org/mixin-deep/-/mixin-deep-1.3.2.tgz",
+      "integrity": "sha512-WRoDn//mXBiJ1H40rqa3vH0toePwSsGb45iInWlTySa+Uu4k3tYUSxa2v1KqAiLtvlrSzaExqS1gtk96A9zvEA==",
       "dev": true,
       "requires": {
         "for-in": "^1.0.2",