add action to build code after each commit

You can download the build artifact from the "Actions->Code Build"

Fixes #129

.github/workflows/build.yml

@@ -0,0 +1,35 @@
+name: Code Build
+
+on:
+  push:
+    branches: [ master ]
+
+jobs:
+  build:
+    name: Build
+    runs-on: ubuntu-latest
+    steps:
+
+    - name: Set up Go 1.14
+      uses: actions/setup-go@v2
+      with:
+        go-version: 1.14
+      id: go
+
+    - name: Check out code into the Go module directory
+      uses: actions/checkout@v2
+
+    - name: Build SFTPGo
+      run: go build -i -ldflags "-s -w -X github.com/drakkan/sftpgo/version.commit=`git describe --always --dirty` -X github.com/drakkan/sftpgo/version.date=`date -u +%FT%TZ`" -o sftpgo
+
+    - run: mkdir output
+    - run: cp sftpgo output/
+    - run: cp sftpgo.json output/
+    - run: cp -r templates output/
+    - run: cp -r static output/
+
+    - name: Upload artifact
+      uses: actions/upload-artifact@v2
+      with:
+        name: sftpgo-build
+        path: output