Set up CI action to run tests

This adds a test matrix for Go 1.17--1.20.

It also adds a README status badge, *of course.*

.github/workflows/release.yml

@@ -1,4 +1,4 @@
-name: Release Docsim
+name: Release
 
 on:
   workflow_dispatch:
@@ -12,12 +12,12 @@ jobs:
     runs-on: ubuntu-latest
 
     steps:
-      - name: Check out code into the Go module directory
+      - name: Check out code
         uses: actions/checkout@v3
         with:
           fetch-depth: 0
 
-      - name: Set up Go 1.19
+      - name: Install Go 1.19
         uses: actions/setup-go@v4
         with:
           go-version: 1.19

.github/workflows/test.yml

@@ -0,0 +1,28 @@
+name: Tests
+on: [push, pull_request]
+permissions: {}
+
+jobs:
+  build:
+    runs-on: ubuntu-latest
+    strategy:
+      matrix:
+        go_version:
+          - "1.17"
+          - "1.18"
+          - "1.19"
+          - "1.20"
+
+    steps:
+      - name: Check out code
+        uses: actions/checkout@v3
+        with:
+          fetch-depth: 0
+
+      - name: Install Go
+        uses: actions/setup-go@v4
+        with:
+          go-version: ${{ matrix.go_version }}
+
+      - name: Run tests
+        run: 'make && make test'

README.md

@@ -1,5 +1,8 @@
 # `docsim`
 
+[![License: GPL v3](https://img.shields.io/badge/License-GPL%20v3-blue.svg)](https://www.gnu.org/licenses/gpl-3.0)
+[![CI Status](https://github.com/hrs/docsim/actions/workflows/test.yml/badge.svg?branch=main)](https://github.com/hrs/docsim/actions/workflows/test.yml)
+
 A simple, fast command-line tool for scoring the similarity of text documents.
 
 ``` console