Switch build to GitHub Actions

- add CI.yml
- remove travis.yml
- change build badge in README.md

.github/workflows/CI.yml

@@ -0,0 +1,20 @@
+name: CI
+
+on:
+    pull_request:
+      branches: [main]
+    push:
+      branches: [main]
+
+jobs:
+  build:
+
+    runs-on: ubuntu-latest
+
+    steps:
+    - uses: actions/checkout@v2
+    - uses: actions/setup-node@v1
+      with:
+        node-version: '12'
+    - run: yarn install --frozen-lockfile
+    - run: yarn ci

.travis.yml

@@ -1,5 +0,0 @@
-language: node_js
-node_js: node
-cache: yarn
-script:
-  - yarn ci

README.md

@@ -1,7 +1,7 @@
 # <img height="86" width="86" alt="React-RxJS Logo" src="assets/logo-128.png" /> React-RxJS: React bindings for RxJS
 
 <!-- prettier-ignore-start -->
-[![Build Status](https://img.shields.io/travis/re-rxjs/react-rxjs.svg?style=flat-square)](https://travis-ci.org/re-rxjs/react-rxjs)
+[![Build Status](https://img.shields.io/github/workflow/status/re-rxjs/react-rxjs/CI?style=flat-square)](https://github.com/re-rxjs/react-rxjs/actions)
 [![codecov](https://img.shields.io/codecov/c/github/re-rxjs/react-rxjs.svg?style=flat-square)](https://codecov.io/gh/re-rxjs/react-rxjs)
 [![version](https://img.shields.io/npm/v/react-rxjs.svg?style=flat-square)](https://www.npmjs.com/package/react-rxjs)
 [![MIT License](https://img.shields.io/npm/l/react-rxjs.svg?style=flat-square)](https://github.com/re-rxjs/react-rxjs/blob/main/LICENSE)