Add workflow for version releases.

This should allow creating a release by simply pushing a tag of the
form "vX.Y.Z" (where "X.Y.Z" follows https://semver.org).

See https://github.com/marketplace/actions/automatic-releases for
more information on the workflow.

.github/workflows/tag_release.yml

@@ -0,0 +1,29 @@
+name: "Tagged release"
+
+on:
+  push:
+    tags:
+      - "v*"
+
+jobs:
+  gh_pre_release:
+    runs-on: "ubuntu-latest"
+    steps:
+      - name: "Checkout source code"
+        uses: "actions/checkout@v2"
+
+      - name: "Install Linux deps"
+        run: |
+          sudo apt install gettext-base psmisc bsdmainutils tar
+
+      - name: "Creating the archive"
+        run: |
+          ./utils/archive.sh
+
+      - uses: "marvinpinto/action-automatic-releases@latest"
+        with:
+          repo_token: "${{ secrets.GITHUB_TOKEN }}"
+          prerelease: false
+          files: |
+            LICENSE
+            GameShell.sh