Enable Github Actions for testing

.github/workflows/test.yml

@@ -0,0 +1,20 @@
+on: [push, pull_request]
+
+name: Actions CI
+
+jobs:
+  build_and_test:
+    name: yup-oauth2 
+    runs-on: ubuntu-latest
+    steps:
+      - uses: actions/checkout@v2
+      - uses: actions-rs/toolchain@v1
+        with:
+          toolchain: stable
+      - uses: actions-rs/cargo@v1
+        with:
+          command: test
+      - uses: actions-rs/cargo@v1
+        with:
+          command: build
+          args: --examples