Attempt to add Discord notification on CI run

Author: hrutvik

.github/workflows/pure.yml

@@ -231,3 +231,24 @@ jobs:
         gh release create ${{ env.VERSION }} --repo cakeml/pure --latest --notes-file $COMMITS pure.S
         rm -f pure.S $COMMITS
 
+  notify:
+    needs: build
+    runs-on: self-hosted
+    container: ubuntu:20.04
+    if: ${{ always() }}
+
+    steps:
+      - name: Notify CakeML Discord
+        run: >
+          curl --silent --show-error --request POST
+            --header "Content-type: application/json;charset=utf-8"
+            --data "{\"embeds\": [{
+                \"title\": \"CI #${{ github.run_number }}\",
+                \"description\": \"${{ needs.build.result == 'success' && 'Passed' || 'Failed' }}\",
+                \"url\": \"https://github.com/CakeML/pure/actions/runs/${{ github.run_id }}\",
+                \"color\": ${{ needs.build.result == 'success' && 8311585 || 13632027 }},
+                \"author\": {
+                  \"name\": \"PureCake CI\",
+                  \"url\": \"https://github.com/CakeML/pure/actions/workflows/pure.yml\"}
+                }]}"
+          ${{ secrets.DISCORD_WEBHOOK }}