add github-actions pipeline

Signed-off-by: Christian Kotzbauer <christian.kotzbauer@gmail.com>

.github/workflows/main.yml

@@ -0,0 +1,21 @@
+name: build
+
+on:
+  push:
+    branches:
+      - '**'
+
+jobs:
+  build:
+    runs-on: ubuntu-latest
+    steps:
+      - name: Install Go
+        uses: actions/setup-go@v2
+        with:
+          go-version: '1.15.2'
+      - name: Checkout
+        uses: actions/checkout@v2
+        with:
+          fetch-depth: "0"
+      - name: Build
+        run: make build-cross

README.md

@@ -1,6 +1,8 @@
 
 # K8sPolicy
 
+![build](https://github.com/ckotzbauer/k8spolicy/workflows/build/badge.svg)
+
 This cli-tool helps you to run rego-policies against your kubernetes yaml-files. Helm-Charts are supported as well. [Conftest](https://github.com/instrumenta/conftest) is used under the hood.
 
 ## Installation