add some basic CI

.github/workflows/ci.yaml

@@ -0,0 +1,24 @@
+on:
+    pull_request:
+    push:
+      branches:
+        - master 
+
+jobs:
+    test:
+        runs-on: ubuntu-20.04
+        steps:
+          - uses: actions/checkout@v2
+            with:
+                fetch-depth: 0
+
+          - name: setup-zig
+            uses: mlugg/setup-zig@v1
+            with:
+                version: 0.13.0
+
+          - name: build
+            run: zig build
+
+          - name: test
+            run: zig build test --summary all