Add release workflow

This workflow compiles syntaxdot-ffi and creates an archive with the
shared library, header, and protobuf file.

.github/workflows/release.yml

@@ -0,0 +1,52 @@
+name: Release
+
+on:
+  push:
+    tags:
+      - '*'
+
+jobs:
+  release:
+    runs-on: ubuntu-16.04
+    steps:
+      - uses: actions/checkout@v1
+      - name: Get release version
+        run: echo ::set-env name=TAG_NAME::$(echo ${GITHUB_REF:10})
+      - name: Install dependencies
+        run: sudo apt-get install cmake pkg-config libssl-dev
+      - uses: actions-rs/toolchain@v1
+        with:
+          profile: minimal
+          toolchain: stable
+          override: true
+      - uses: actions-rs/cargo@v1
+        with:
+          command: build
+          args: --release
+      - name: Create release archive
+        id: create_archive
+        run: |
+          DIST=syntaxdot-ffi-${TAG_NAME}-x86_64-linux-gnu-gcc
+          ARCHIVE=${DIST}.tar.gz
+          install -Dm755 -t ${DIST}/lib target/release/libsyntaxdot_ffi.so
+          install -Dm644 -t ${DIST}/include include/syntaxdot.h
+          install -Dm644 -t ${DIST}/share/syntaxdot/proto proto/syntaxdot.proto
+          tar -czvf ${ARCHIVE} ${DIST}
+          echo ::set-output name=ASSET::$ARCHIVE
+      - uses: actions/[email protected]
+        id: create_release
+        env:
+          GITHUB_TOKEN: ${{ secrets.GITHUB_TOKEN }}
+        with:
+          tag_name: ${{ github.ref }}
+          release_name: Release ${{ github.ref }}
+          draft: true
+          prerelease: false
+      - uses: actions/[email protected]
+        env:
+          GITHUB_TOKEN: ${{ secrets.GITHUB_TOKEN }}
+        with:
+          upload_url: ${{ steps.create_release.outputs.upload_url }}
+          asset_path: ${{ steps.create_archive.outputs.ASSET }}
+          asset_name: ${{ steps.create_archive.outputs.ASSET }}
+          asset_content_type: application/gzip