build: use htmlpreview.github.com for simpler report publishing

Author: nedbat

.github/workflows/coverage.yml

@@ -178,7 +178,7 @@ jobs:
           echo "sha10=$SHA10" >> $GITHUB_ENV
           echo "slug=$SLUG" >> $GITHUB_ENV
           echo "report_dir=$REPORT_DIR" >> $GITHUB_ENV
-          echo "url=https://nedbat.github.io/coverage-reports/$REPORT_DIR" >> $GITHUB_ENV
+          echo "url=https://htmlpreview.github.io/?https://github.com/nedbat/coverage-reports/blob/main/reports/$SLUG/htmlcov/index.html" >> $GITHUB_ENV
           echo "branch=${REF#refs/heads/}" >> $GITHUB_ENV
 
       - name: "Summarize"
@@ -217,6 +217,8 @@ jobs:
           # Make the commit message.
           echo "${{ env.total }}% - $COMMIT_MESSAGE" > commit.txt
           echo "" >> commit.txt
+          echo "[View the report](${{ env.url }})" >> commit.txt
+          echo "" >> commit.txt
           echo "${{ env.url }}" >> commit.txt
           echo "${{ env.sha10 }}: ${{ env.branch }}" >> commit.txt
           # Commit.