DEV: Merge root JS packages (#25857)

Before this commit, we had a yarn package set up in the root directory and also in `app/assets/javascripts`. That meant two `yarn install` calls and two `node_modules` directories. This commit merges them both into the root location, and updates references to node_modules.

A previous attempt can be found at https://github.com/discourse/discourse/pull/21172. This commit re-uses that script to merge the `yarn.lock` files.

Co-authored-by: Jarek Radosz <jradosz@gmail.com>

.github/dependabot.yml

@@ -52,13 +52,25 @@ updates:
           - "railties"
           - "sprockets-rails"
   - package-ecosystem: "npm"
-    directory: "/app/assets/javascripts/"
+    directory: "/"
     schedule:
       interval: daily
       time: "08:00"
       timezone: Australia/Sydney
     open-pull-requests-limit: 20
     versioning-strategy: increase
+    ignore: # These are all vendored so need to be updated manually. See lib/tasks/javascript.rake
+      - dependency-name: "ace-builds"
+      - dependency-name: "@json-editor/json-editor"
+      - dependency-name: "chart.js"
+      - dependency-name: "chartjs-plugin-datalabels"
+      - dependency-name: "diffhtml"
+      - dependency-name: "magnific-popup"
+      - dependency-name: "pikaday"
+      - dependency-name: "moment"
+      - dependency-name: "moment-timezone"
+      - dependency-name: "@discourse/moment-timezon-names-translations"
+      - dependency-name: "squoosh"
     groups:
       babel:
         patterns: