Create source code packages by adding release tags

According to the [GitHub blog](https://github.blog/2023-02-21-update-on-the-future-stability-of-source-code-archives-and-hashes/), files by `git archive` are not guaranteed to have checksum persistence.
It is also stated that the archive file at this time is stable in bytes, but that this may change in the future.

.github/workflows/release.yml

@@ -0,0 +1,46 @@
+name: Release Builds
+
+on:
+  push:
+    tags:
+      - "*.*.*"
+
+permissions: read-all
+
+jobs:
+  source:
+    name: Source Code Releasing
+    if: ${{ github.repository == 'mruby/mruby' }}
+    permissions:
+      contents: write
+    runs-on: ubuntu-22.04
+    timeout-minutes: 10
+    strategy:
+      fail-fast: false
+    steps:
+      - name: "Checkout ${{ github.ref_name }} ( ${{ github.sha }} )"
+        uses: actions/checkout@v4
+      - name: Builds
+        id: builds
+        run: |
+          tagname="$GITHUB_REF_NAME"
+          packagename="mruby-$tagname"
+          destdir=packages
+
+          mkdir -p "$destdir"
+          git archive --format zip --prefix "$packagename/" -o "$destdir/$packagename.zip" "$GITHUB_REF"
+          git archive --format tar.gz --prefix "$packagename/" -o "$destdir/$packagename.tar.gz" "$GITHUB_REF"
+          gunzip -c "$destdir/$packagename.tar.gz" | xz > "$destdir/$packagename.tar.xz"
+
+          (
+            cd "$destdir"
+            sha256sum * > .sha256
+            mv .sha256 "$packagename.sha256"
+          )
+      - name: Release
+        uses: softprops/action-gh-release@v1
+        with:
+          # draft: true
+          prerelease: ${{ contains(github.ref_name, '-rc') }}
+          body_path: NEWS
+          files: packages/*