[add] Triggering coverage test on push/pull_request to repo. Included coverage badge on Readme. (#43)

Author: filipecosta90

.github/workflows/coverage.yml

@@ -0,0 +1,19 @@
+on: [push, pull_request]
+name: Generate coverage report
+jobs:
+  coverage:
+    runs-on: ubuntu-latest
+    steps:
+    - name: Install Go
+      uses: actions/setup-go@v2
+      with:
+        go-version: 1.15.x
+    - name: Checkout code
+      uses: actions/checkout@v2
+    - name: Generate coverage report
+      run: |
+        make coverage
+    - name: Upload coverage to Codecov
+      uses: codecov/codecov-action@v1
+      with:
+        file: ./coverage.txt

README.md

@@ -4,7 +4,8 @@ hdrhistogram-go
 <a href="https://pkg.go.dev/github.com/HdrHistogram/hdrhistogram-go"><img src="https://pkg.go.dev/badge/github.com/HdrHistogram/hdrhistogram-go" alt="PkgGoDev"></a>
 [![Gitter](https://badges.gitter.im/Join_Chat.svg)](https://gitter.im/HdrHistogram/HdrHistogram)
 ![Test](https://github.com/HdrHistogram/hdrhistogram-go/workflows/Test/badge.svg?branch=master)
- [![License: MIT](https://img.shields.io/badge/License-MIT-yellow.svg)](https://github.com/HdrHistogram/hdrhistogram-go/blob/master/LICENSE)
+[![License: MIT](https://img.shields.io/badge/License-MIT-yellow.svg)](https://github.com/HdrHistogram/hdrhistogram-go/blob/master/LICENSE)
+[![Codecov](https://codecov.io/gh/HdrHistogram/hdrhistogram-go/branch/master/graph/badge.svg)](https://codecov.io/gh/HdrHistogram/hdrhistogram-go)
 
 
 A pure Go implementation of the [HDR Histogram](https://github.com/HdrHistogram/HdrHistogram).