feat: add GitHub Actions workflow for building and uploading slack_cli artifacts

Author: orestesgaolin

.github/workflows/build_slack.yaml

@@ -0,0 +1,68 @@
+name: Build slack_cli
+
+on:
+  workflow_dispatch:
+  push:
+    tags:
+      - "slack_cli-v[0-9]+.[0-9]+.[0-9]+"
+
+jobs:
+  build_slack_cli:
+    defaults:
+      run:
+        working-directory: slack_cli
+    name: Build slack_cli
+    strategy:
+      matrix:
+        os: [ubuntu-latest, windows-latest, macos-latest, macos-13]
+        include:
+          - binary-name: slack_cli_linux
+            os: ubuntu-latest
+          - binary-name: slack_cli.exe
+            os: windows-latest
+          - binary-name: slack_cli_macos
+            os: macos-latest
+          - binary-name: slack_cli_macos_x86
+            os: macos-13
+    runs-on: ${{ matrix.os }}
+    steps:
+      - uses: actions/checkout@v4
+      - uses: dart-lang/setup-dart@v1
+      - run: dart pub get
+      - run: mkdir build
+      - run: mkdir build/${{ matrix.os }}
+      - run: dart compile exe bin/slack_cli.dart -o build/${{ matrix.os }}/${{ matrix.binary-name }}
+      - uses: actions/upload-artifact@v4
+        with:
+          name: bin-${{ matrix.os }}
+          path: slack_cli/build/${{ matrix.os }}/${{ matrix.binary-name }}
+
+  upload_artifacts:
+    needs: build_slack_cli
+    name: Upload Artifacts to GitHub Release
+    runs-on: ubuntu-latest
+    permissions:
+      contents: write
+    steps:
+      - uses: actions/download-artifact@v4
+        with:
+          name: bin-ubuntu-latest
+          path: bin-linux
+      - uses: actions/download-artifact@v4
+        with:
+          name: bin-macos-latest
+          path: bin-macos
+      - uses: actions/download-artifact@v4
+        with:
+          name: bin-windows-latest
+          path: bin-windows
+      - uses: actions/download-artifact@v4
+        with:
+          name: bin-macos-13
+          path: bin-macos-x86
+      
+      - name: Upload artifacts to existing release
+        uses: softprops/action-gh-release@v1
+        with:
+          files: bin-*/*
+          draft: false  # Publish the release after artifacts are uploaded