Add workflow to build source package

.github/workflows/submit.yml

@@ -0,0 +1,41 @@
+on:
+  push:
+    branches:
+      - master
+  workflow_dispatch:
+
+name: Submit to launchpad
+
+jobs:
+  Build:
+    runs-on: ubuntu-24.04
+    name: 'Submit to Launchpad'
+
+    steps:
+      - name: Prepare system
+        run: |
+          sudo apt-get update
+          sudo add-apt-repository -y "ppa:marutter/rrutter4.0"
+          sudo apt-get install -y git gnupg curl devscripts equivs gdebi-core
+          systemctl --user status gpg-agent || true
+          systemctl --user stop gpg-agent || true
+          systemctl --user start gpg-agent || true
+
+      - name: Checkout
+        uses: actions/checkout@v4
+
+      - name: Install build dependencies
+        run: |
+          sudo mk-build-deps -i
+
+      - name: Build and sign source package
+        run: |
+          echo "DEBUILD_TGZ_CHECK=no" >> ~/.devscripts
+          curl -sSL $GPG_KEY > private.pgp
+          export GPG_TTY=$(tty)
+          echo $GPG_PASS | gpg --batch --yes --pinentry-mode loopback --passphrase-fd 0 --import private.pgp
+          rm -f private.pgp
+          debuild -S -i -I
+        env:
+          GPG_KEY: ${{ secrets.GPG_KEY }}
+          GPG_PASS: ${{ secrets.GPG_PASS }}