Add a github action to test bitvec

Author: erickt

.github/workflows/ci.yml

@@ -0,0 +1,41 @@
+name: All Tests
+
+on:
+  pull_request:
+  push:
+    branches:
+      - master
+
+jobs:
+  test:
+    name: Test
+    runs-on: ${{ matrix.os }}
+    strategy:
+      matrix:
+        os: ubuntu-latest
+        rust:
+          - stable
+          - beta
+          - nightly
+          - "1.63"
+    steps:
+      - uses: actions/checkout@v1
+      - uses: dtolnay/rust-toolchain@master
+        with:
+          toolchain: ${{ matrix.rust }}
+      - run: cargo test
+
+  docs:
+    name: docs
+    runs-on: ubuntu-latest
+    steps:
+      - uses: actions/checkout@v1
+      - uses: dtolnay/rust-toolchain@master
+        with:
+          toolchain: stable
+          components: clippy
+
+      - name: Check documentation
+        env:
+          RUSTDOCFLAGS: -D warnings
+        run: cargo doc --no-deps --document-private-items --workspace