docs: bundle assets with Hugo

Also:

* load any docs' third-party dependencies from node_modules (except for examples)
* exclude docsearch from layouts that don't use it
* preconnect to algolia only when not examples layout
* switch to `RelPermalink`
* refactor JS assets into partials

.eslintrc.json

@@ -197,6 +197,15 @@
         "unicorn/no-array-for-each": "off"
       }
     },
+    {
+      "files": [
+        "site/assets/js/**"
+      ],
+      "parserOptions": {
+        "sourceType": "module",
+        "ecmaVersion": 2020
+      }
+    },
     {
       "files": [
         "**/*.md"