tc-build: Add GitHub Actions workflow

Makes sure that shell scripts are clean through shellcheck and Python
scripts are run through YAPF. This ensures that the code base stays high
quality and consistent.

Signed-off-by: Nathan Chancellor <natechancellor@gmail.com>

.github/workflows/main.yml

@@ -0,0 +1,18 @@
+# Run a couple of linters on code in repo
+# * shellcheck for shell scripts
+# * YAPF for Python scripts
+name: Lint checks
+on: [push, pull_request]
+jobs:
+  shellcheck:
+    runs-on: ubuntu-latest
+    steps:
+    - uses: actions/checkout@v2
+    - name: shellcheck
+      uses: bewuethr/shellcheck-action@v1
+  yapf:
+    runs-on: ubuntu-latest
+    steps:
+    - uses: actions/checkout@v2
+    - name: yapf
+      uses: AlexanderMelde/yapf-action@master