New broken link report (#16412)

* add linkinator npm package

* add new script that uses Linkinator

* reorg the excluded links file and update comments

* replace blc artifacts with linkinator artifacts in .gitignore

* update the scheduled workflow to use the new script

* dismantle BLC scripts

* add workflow_dispatch event so we can test this manually

* npm uninstall broken-link-checker

* use different exit codes depending on whether broken links are found

.github/workflows/check-all-english-links.yml

@@ -1,6 +1,7 @@
 name: Check all English links
 
 on:
+  workflow_dispatch:
   schedule:
     - cron:  "40 19 * * *" # once a day at 19:40 UTC / 11:40 PST
 
@@ -10,21 +11,16 @@ jobs:
     if: github.repository == 'github/docs-internal'
     runs-on: ubuntu-latest
     steps:
-    - uses: actions/checkout@5a4ac9002d0be2fb38bd78e4b4dbde5606d7042f
-    - name: npm ci
-      run: npm ci
-    - name: npm run build
-      run: npm run build
     - name: Run script
-      run: script/check-external-links en > broken_links.md
+      run: script/check-english-links > broken_links.md
     - name: Check if any broken links
       id: check
       run: |
-        if [ "$(grep 'All links are good' broken_links.md)" ]; then
+        if [ "$(grep '0 broken links found' broken_links.md)" ]; then
           echo ::set-output name=continue::no
         else
           echo "::set-output name=continue::yes"
-          echo "::set-output name=title::$(grep 'found on help.github.com' broken_links.md)"
+          echo "::set-output name=title::$(head -1 broken_links.md)"
         fi
     - if: ${{ steps.check.outputs.continue == 'yes' }}
       name: Create issue from file