Improve commit to gh-pages (#155)

* Use `github-actions[bot]` as commiter to gh-pages

to avoid the intermittent failure of the email of ${{github.actor}} not
being found, causing the build to fail

* Add the trigger commit to gh-pages commit message

to make it easier to correlate the new version of the page with the
change in the spec that triggered it

.github/workflows/build.yml

@@ -152,11 +152,12 @@ jobs:
         if: github.ref == 'refs/heads/master'
 
         run: |
-            git config --local user.name ${{ github.actor }}
+            git config user.name 'github-actions[bot]'
+            git config user.email 'github-actions[bot]@users.noreply.github.com'
             git add index.html
             git add pdfs
             git add html
-            git commit -m "Updated"
+            git commit -m "Updated for ${{ github.sha }}"
 
 
       - name: Push to gh-pages