Add update workflow to account for beta branch

.github/workflows/update.yaml

@@ -0,0 +1,26 @@
+name: Check for updates
+on:
+  schedule:
+    - cron: '0 * * * *'
+  workflow_dispatch: {}
+jobs:
+  flatpak-external-data-checker:
+    runs-on: ubuntu-latest
+    strategy:
+      matrix:
+        branch: [ master, beta ]
+    steps:
+      - uses: actions/checkout@v3
+        with:
+          ref: ${{ matrix.branch }}
+      - uses: docker://ghcr.io/flathub/flatpak-external-data-checker:latest
+        env:
+          GIT_AUTHOR_NAME: Flatpak External Data Checker
+          GIT_COMMITTER_NAME: Flatpak External Data Checker
+          GIT_AUTHOR_EMAIL: 41898282+github-actions[bot]@users.noreply.github.com
+          GIT_COMMITTER_EMAIL: 41898282+github-actions[bot]@users.noreply.github.com
+          EMAIL: 41898282+github-actions[bot]@users.noreply.github.com
+          GITHUB_TOKEN: ${{ secrets.GITHUB_TOKEN }}
+        with:
+          entrypoint: /bin/bash
+          args: -c "git config --global --add safe.directory /github/workspace && cd /github/workspace && /app/flatpak-external-data-checker --update --never-fork com.slack.Slack.yaml"

flathub.json

@@ -1,3 +1,4 @@
 {
-  "only-arches": ["x86_64"]
+  "only-arches": ["x86_64"],
+  "disable-external-data-checker": true
 }