Add support for discussion

Author: khiga8

README.md

@@ -15,12 +15,14 @@ on:
     types: [opened, edited]
   issue_comment:
     types: [created, edited]
+  discussion:
+    types: [created, edited]
 
 jobs:
   accessibility_alt_text_bot:
     name: Check alt text is set on issue or pull requests
     runs-on: ubuntu-latest
-    if: ${{ github.event.issue || github.event.pull_request }}
+    if: ${{ github.event.issue || github.event.pull_request || github.event.discussion }}
     steps:
       - name: Get action 'github/accessibility-alt-text-bot'
         uses: github/accessibility-alt-text-bot