allow running external link-checking manually (#1379)

Author: SethTisue

.github/workflows/ci.yaml

@@ -2,6 +2,7 @@ name: scala-lang docs
 
 on:
   pull_request:
+  workflow_dispatch:
   schedule:
     - cron: '00 0 * * *'
 
@@ -22,11 +23,11 @@ jobs:
           ( ! grep -qie Error -e Warn error.log )
           find ./_site \( -type d \( -name events -o -name training \) -prune -false \) -o \( -type f ! -name error.log -empty \)
           find ./_site \( -type d \( -name events -o -name training \) -prune -false \) -o \( -type f ! -name error.log -empty \) | ( ! read )
-      - name: Proofing (Pull Request)
-        if: ${{ github.event_name != 'schedule' }}
+      - name: Proofing (local links only)
+        if: github.event_name == 'pull_request'
         run: |
           bundle exec htmlproofer ./_site/ --disable-external --only-4xx --empty-alt-ignore --allow-hash-href
-      - name: Proofing (Cron)
-        if: ${{ github.event_name == 'schedule' }}
+      - name: Proofing (all links)
+        if: github.event_name != 'pull_request'
         run: |
           bundle exec htmlproofer ./_site/ --external_only --only-4xx --http-status-ignore "400,401,429" --empty-alt-ignore --allow-hash-href --url-ignore "/trends.google.com/,/pgp.mit.edu/,/www.oracle.com/,/scalafiddle.io/" --typhoeus-config='{"headers":{"Accept-Encoding":"gzip, deflate"}}'