Generate “x-element.d.ts” from JSDoc comments.

Previously, the “x-element.d.ts” file was hand-curated, which was prone
to falling out of date.

Because the TypeScript team manages JSDoc, it’s fairly straightforward
to properly “type” your JS with JSDoc and output declarations which can
be used by folks writing TypeScript — all of that without needing to
actually author TypeScript ourselves.†

Additionally, tools like JSR will build basic documentation for
libraries which author JSDoc comments, so some wins there.

Finally, to ensure best practices for our JSDocs, we enable some
recommended rules from the eslint plugin.

† One goal of “x-element” is to be _highly_ portable, it’s why no
  dependencies exist and why the “x-element.js” file can be used
  _verbatim_ without a build step.

deno.json

@@ -1,5 +1,12 @@
 {
   "name": "@netflix/x-element",
   "version": "1.0.0",
-  "exports": "./x-element.js"
+  "exports": {
+    "./x-element.d.ts": "./x-element.d.ts"
+  },
+  "include": [
+    "./x-element.js",
+    "./x-element.d.ts",
+    "./x-element.d.ts.map"
+  ]
 }

eslint.config.js

@@ -1,7 +1,9 @@
 import globals from 'globals';
+import jsdoc from 'eslint-plugin-jsdoc';
 import NetflixCommon from '@netflix/eslint-config';
 
 export default [
+  jsdoc.configs['flat/recommended'],
   {
     ...NetflixCommon,
     files: ['**/*.js'],
@@ -12,6 +14,15 @@ export default [
       'demo/react/*',
     ],
   },
+  {
+    files: ['x-element.js'],
+    plugins: { jsdoc },
+    rules: {
+      'jsdoc/require-param-description': 'off',
+      'jsdoc/require-property-description': 'off',
+      'jsdoc/require-returns-description': 'off',
+    },
+  },
   {
     ...NetflixCommon,
     files: ['demo/react/**/*.js'],