ci: add build workflow and README badges (#1)

* ci: add build workflow

Features:
- a workflow to build / test the project and calculate test coverage on every:
  - push to main 
  - new PR to main created
  - commit added to a PR targeting main
- project documentation badges in README.md

.github/workflows/build.yml

@@ -0,0 +1,35 @@
+# This workflow will build a golang project
+# For more information see: https://docs.github.com/en/actions/automating-builds-and-tests/building-and-testing-go
+
+name: build
+
+on:
+  push:
+    branches: [ "main" ]
+  pull_request:
+    branches: [ "main" ]
+
+jobs:
+
+  build:
+    runs-on: ${{ matrix.os }}
+    strategy:
+      matrix:
+        os: [ ubuntu-latest ]
+    steps:
+    - uses: actions/checkout@v3
+
+    - uses: actions/setup-go@v4
+      with:
+        go-version: '1.18'
+
+    - name: Build
+      run: go build -v ./...
+
+    - name: Test with coverage
+      run: go test -v -race -covermode=atomic -coverprofile=coverage.out ./...
+
+    - name: Upload coverage reports to Codecov
+      uses: codecov/codecov-action@v3
+      env:
+        CODECOV_TOKEN: ${{ secrets.CODECOV_TOKEN }}

README.md

@@ -1,5 +1,10 @@
 # nb
 
+[![Build status](https://github.com/bevzzz/nb/actions/workflows/build.yml/badge.svg?branch=ci)](https://github.com/bevzzz/nb/actions/workflows/build.yml?query=branch%3Amain)
+[![Go Reference](https://pkg.go.dev/badge/github.com/bevzzz/nb.svg)](https://pkg.go.dev/github.com/bevzzz/nb)
+[![Go Report Card](https://goreportcard.com/badge/github.com/bevzzz/nb)](https://goreportcard.com/report/github.com/bevzzz/nb)
+[![codecov](https://codecov.io/gh/bevzzz/nb/branch/main/graph/badge.svg?token=BS7XDXHA21)](https://codecov.io/gh/bevzzz/nb/tree/main)
+
 	Render Jupyter Notebooks in pure Go 📔
 
 This package is inspired by @yuin's [`goldmark`](https://github.com/yuin/goldmark) and is designed to be as clear and extensible.