Added CI and dependabot

.github/dependabot.yml

@@ -0,0 +1,6 @@
+version: 2
+updates:
+  - package-ecosystem: "github-actions"
+    directory: "/"
+    schedule:
+      interval: "weekly"

.github/workflows/pipelines.yml

@@ -0,0 +1,53 @@
+name: CI
+
+on: [push]
+
+jobs:
+  flatpak:
+    name: Flatpak
+    runs-on: ubuntu-22.04
+
+    strategy:
+      matrix:
+        arch: [x86_64, aarch64]
+      # Don't fail the whole workflow if one architecture fails
+      fail-fast: false
+
+    container:
+      image: ghcr.io/elementary/flatpak-platform/runtime:8-${{ matrix.arch }}
+      options: --privileged
+
+    steps:
+      - name: Checkout
+        uses: actions/checkout@v4
+
+      - name: Set up QEMU for aarch64 emulation
+        if: ${{ matrix.arch != 'x86_64' }}
+        uses: docker/setup-qemu-action@v3
+        with:
+          platforms: arm64
+
+      - name: Build
+        uses: flatpak/flatpak-github-actions/flatpak-builder@v6
+        with:
+          bundle: reco.flatpak
+          manifest-path: build-aux/appcenter/com.github.gijsgoudzwaard.image-optimizer.yml
+          run-tests: true
+          repository-name: appcenter
+          repository-url: https://flatpak.elementary.io/repo.flatpakrepo
+          cache-key: "flatpak-builder-${{ github.sha }}"
+          arch: ${{ matrix.arch }}
+
+  lint:
+    name: Lint
+    runs-on: ubuntu-22.04
+
+    container:
+      image: valalang/lint
+
+    steps:
+      - name: Checkout
+        uses: actions/checkout@v4
+
+      - name: Lint
+        run: io.elementary.vala-lint -d .