add github actions tests

Was chatting with @brandonweeks who mentioned go-tpm uses a different CI
and expressed interest in github actions.

.github/workflows/test.yml

@@ -0,0 +1,16 @@
+on: [push, pull_request]
+name: Test
+jobs:
+  test:
+    strategy:
+      matrix:
+        go-version: [1.19.x, 1.20.x]
+        os: [ubuntu-latest, macos-latest, windows-latest]
+    runs-on: ${{ matrix.os }}
+    steps:
+    - uses: actions/setup-go@v3
+      with:
+        go-version: ${{ matrix.go-version }}
+    - uses: actions/checkout@v3
+    - run: go build ./...
+    - run: go test ./...