ci: use GitHub Apps (#128)

It seems that using GitHub Apps is best practice for it.

Signed-off-by: Kentaro Hayashi <hayashi@clear-code.com>

Author: kenhys

.github/workflows/add-to-project.yml

@@ -10,8 +10,15 @@ jobs:
     name: Add issue to project
     runs-on: ubuntu-latest
     steps:
+      - name: Generate token
+        id: generate_token
+        uses: actions/create-github-app-token@f8d387b68d61c58ab83c6c016672934102569859 # v3.0.0
+        with:
+          app-id: ${{ secrets.PROJECT_APP_ID }}
+          private-key: ${{ secrets.PROJECT_APP_PRIVATE_KEY }}
+          owner: fluent
       - uses: actions/add-to-project@244f685bbc3b7adfa8466e08b698b5577571133e # v1.0.2
         with:
           project-url: https://github.com/orgs/fluent/projects/4
-          github-token: ${{ secrets.ADD_TO_PROJECT_PAT }}
+          github-token: ${{ steps.generate_token.outputs.token }}
           labeled: waiting-for-triage