Restore files deleted in merge

diff --git a/.github/workflows/ci.yml b/.github/workflows/ci.yml
new file mode 100644
index 0000000..0994653
--- /dev/null
+++ b/.github/workflows/ci.yml

@@ -0,0 +1,37 @@
+# This workflow uses actions that are not certified by GitHub.
+# They are provided by a third-party and are governed by
+# separate terms of service, privacy policy, and support
+# documentation.
+
+name: ci
+
+on:
+  push:
+    branches: [ master ]
+  pull_request:
+    branches: [ master ]
+
+jobs:
+  analyze:
+    runs-on: ubuntu-latest
+
+    steps:
+      - uses: actions/checkout@v2
+      - uses: dart-lang/setup-dart@v1.0
+        with:
+          sdk: dev
+      - run: pub get
+      - run: dart format --output=none --set-exit-if-changed .
+      - run: dart analyze --fatal-infos
+  test:
+    runs-on: ubuntu-latest
+    strategy:
+      matrix:
+        sdk: [2.12.0, stable, dev]
+    steps:
+      - uses: actions/checkout@v2
+      - uses: dart-lang/setup-dart@v1.0
+        with:
+          sdk: ${{ matrix.sdk }}
+      - run: pub get
+      - run: pub run test -p vm,chrome

diff --git a/.gitignore b/.gitignore
new file mode 100644
index 0000000..e43b40f
--- /dev/null
+++ b/.gitignore

@@ -0,0 +1,9 @@
+# Files and directories created by pub
+.dart_tool/
+.packages
+.pub/
+packages
+pubspec.lock
+
+# Directory created by dartdoc
+doc/api/

diff --git a/CONTRIBUTING.md b/CONTRIBUTING.md
new file mode 100644
index 0000000..6f5e0ea
--- /dev/null
+++ b/CONTRIBUTING.md

@@ -0,0 +1,33 @@
+Want to contribute? Great! First, read this page (including the small print at
+the end).
+
+### Before you contribute
+Before we can use your code, you must sign the
+[Google Individual Contributor License Agreement](https://cla.developers.google.com/about/google-individual)
+(CLA), which you can do online. The CLA is necessary mainly because you own the
+copyright to your changes, even after your contribution becomes part of our
+codebase, so we need your permission to use and distribute your code. We also
+need to be sure of various other things—for instance that you'll tell us if you
+know that your code infringes on other people's patents. You don't have to sign
+the CLA until after you've submitted your code for review and a member has
+approved it, but you must do it before we can put your code into our codebase.
+
+Before you start working on a larger contribution, you should get in touch with
+us first through the issue tracker with your idea so that we can help out and
+possibly guide you. Coordinating up front makes it much easier to avoid
+frustration later on.
+
+### Code reviews
+All submissions, including submissions by project members, require review.
+
+### File headers
+All files in the project must start with the following header.
+
+    // Copyright (c) 2015, the Dart project authors.  Please see the AUTHORS file
+    // for details. All rights reserved. Use of this source code is governed by a
+    // BSD-style license that can be found in the LICENSE file.
+
+### The small print
+Contributions made by corporations are covered by a different agreement than the
+one above, the
+[Software Grant and Corporate Contributor License Agreement](https://developers.google.com/open-source/cla/corporate).