feat: add support for YouTube Kids (#291)

* dev: add `WEB_KIDS` innertube client

* refactor: move DASH manifest stuff out of `VideoInfo`
This makes it easier to use these functions elsewhere.

* feat(ytkids): add `Kids#getInfo()` & `Kids#search()`

* feat: add `Innertube#kids.getHomeFeed()`

* docs: add YouTube Kids API ref

* docs: fix typo

* docs: fix yet another typo

* docs: update YouTube Music API ref
Unrelated but required to reflect changes made to the DASH manifest generation functions

* chore: lint

* chore: add tests

* feat: include `captions` in `VideoInfo`

* chore: fix tests

src/utils/HTTPClient.ts

@@ -40,8 +40,8 @@ export default class HTTPClient {
 
     const headers =
       init?.headers ||
-        (input instanceof Request ? input.headers : new Headers()) ||
-        new Headers();
+      (input instanceof Request ? input.headers : new Headers()) ||
+      new Headers();
 
     const body = init?.body || (input instanceof Request ? input.body : undefined);
 
@@ -65,6 +65,7 @@ export default class HTTPClient {
     const content_type = request_headers.get('Content-Type');
 
     let request_body = body;
+    let is_web_kids = false;
 
     const is_innertube_req =
       baseURL === innertube_url ||
@@ -85,11 +86,12 @@ export default class HTTPClient {
 
       delete n_body.client;
 
+      is_web_kids = n_body.context.client.clientName === 'WEB_KIDS';
       request_body = JSON.stringify(n_body);
     }
 
-    // Authenticate
-    if (this.#session.logged_in && is_innertube_req) {
+    // Authenticate (NOTE: YouTube Kids does not support regular bearer tokens)
+    if (this.#session.logged_in && is_innertube_req && !is_web_kids) {
       const oauth = this.#session.oauth;
 
       if (oauth.validateCredentials()) {
@@ -157,6 +159,40 @@ export default class HTTPClient {
         ctx.client.clientScreen = 'EMBED';
         ctx.thirdParty = { embedUrl: Constants.URLS.YT_BASE };
         break;
+      case 'YTKIDS':
+        ctx.client.clientVersion = Constants.CLIENTS.WEB_KIDS.VERSION;
+        ctx.client.clientName = Constants.CLIENTS.WEB_KIDS.NAME;
+        ctx.client.kidsAppInfo = { // TODO: Make this customizable
+          categorySettings: {
+            enabledCategories: [
+              'approved_for_you',
+              'black_joy',
+              'camp',
+              'collections',
+              'earth',
+              'explore',
+              'favorites',
+              'gaming',
+              'halloween',
+              'hero',
+              'learning',
+              'move',
+              'music',
+              'reading',
+              'shared_by_parents',
+              'shows',
+              'soccer',
+              'sports',
+              'spotlight',
+              'winter'
+            ]
+          },
+          contentSettings: {
+            corpusPreference: 'KIDS_CORPUS_PREFERENCE_YOUNGER',
+            kidsNoSearchMode: 'YT_KIDS_NO_SEARCH_MODE_OFF'
+          }
+        };
+        break;
       default:
         break;
     }