Add CI builds with GitHub Actions

This configures linter, tests and build to run on merges to master and
on PRs against master. #9

.github/workflows/ci-build.yml

@@ -0,0 +1,27 @@
+name: facilitator-ci-build
+
+on:
+  push:
+    branches: [ main ]
+  pull_request:
+    branches: [ main ]
+  workflow_dispatch:
+
+env:
+  CARGO_TERM_COLOR: always
+
+defaults:
+  run:
+    working-directory: facilitator
+
+jobs:
+  build-rust:
+    runs-on: ubuntu-latest
+    steps:
+    - uses: actions/checkout@v2
+    - name: Lint
+      run: cargo fmt --message-format human -- --check
+    - name: Build
+      run: cargo build --verbose
+    - name: Run tests
+      run: cargo test --verbose