Add github action for automatic build on release

.github/workflows/build_release.yaml

@@ -0,0 +1,31 @@
+# Controls when the workflow will run
+on:
+  push:
+    tags:
+	- "v*"
+  # Allows you to run this workflow manually from the Actions tab
+  workflow_dispatch:
+
+jobs:
+  # This workflow contains a single job called "build"
+  build:
+    # The type of runner that the job will run on
+    runs-on: ubuntu-latest
+
+    steps:
+      - uses: actions/checkout@v2
+      - uses: haskell/actions/setup@v1
+      	enable-stack: true
+
+      - name: build executable
+        run: |
+	  stack build
+          find .stack-work/install -name oschark -exec mv {} . \;
+      - name: do Release
+        uses: softprops/action-gh-release@v1
+      	with:
+	  prerelease: true
+	  files: |
+	  oschark
+	  LICENSE
+