Add basic Bazel build/test CI matrix for Ubuntu

Signed-off-by: Evan Flynn <evan.flynn@apex.ai>

.github/workflows/build_test.yml

@@ -0,0 +1,35 @@
+name: Build/Test
+
+on:
+  push:
+    branches:
+      - main
+    tags:
+      - "**"
+  pull_request:
+    branches:
+      - main
+  workflow_dispatch:
+
+# only run one build doc workflow at a time, cancel any running ones
+concurrency: 
+  group: ${{ github.workflow }}-${{ github.ref }}
+  cancel-in-progress: true
+
+jobs:
+  build_test:
+    strategy:
+      matrix:
+        os:
+          - ubuntu
+        version:
+          - 18.04
+          - 20.04
+          - 22.04
+    runs-on: ${{ matrix.os }}
+    steps:
+      - uses: actions/checkout@v2
+      - name: Build
+        run: bazel build //...
+      - name: Test
+        run: bazel test //...