Add unit tests and report coverage

.eslintrc.json

@@ -1,5 +1,6 @@
 {
     "env": {
+        "jest": true,
         "browser": true,
         "es2021": true
     },

.github/workflows/action.yml

@@ -21,3 +21,7 @@ jobs:
         run: npm run lint
       - name: test
         run: npm run test
+      - name: coverage
+        uses: coverallsapp/github-action@master
+        with:
+          github-token: ${{ secrets.GITHUB_TOKEN }}

README.md

@@ -1,14 +1,19 @@
 # homeassistant-js-yaml-schema
+
+[![Coverage Status](https://coveralls.io/repos/github/pascalre/homeassistant-js-yaml-schema/badge.svg?branch=master)](https://coveralls.io/github/pascalre/homeassistant-js-yaml-schema?branch=master)
+
 Schema to allow js-yaml to process YAML formatted Home Assistent templates that use Home Assistent specific [local tags](https://www.home-assistant.io/docs/configuration/splitting_configuration/) while parsing or dumping, for example: `!env_var`, `!include_dir_named`.
 
 See [tags.json](https://github.com/pascalre/homeassistant-js-yaml-schema/blob/master/src/tags.json) for currently supported local tags.
 
 # Usage
 ```typescript
-import * as jsyaml from "js-yaml"
+const jsyaml = require('js-yaml');
+const fs     = require('fs');
 import { HOMEASSISTANT_SCHEMA } from "homeassistant-js-yaml-schema"
 
-let body = jsyaml.load(yamlDocument, { schema: HOMEASSISTANT_SCHEMA });
+let doc = yaml.load(fs.readFileSync('/path/to/file.yml', 'utf8'));
+let body = jsyaml.load(doc, { schema: HOMEASSISTANT_SCHEMA });
 console.log(JSON.stringify(body, null, 2));
 
 body = jsyaml.dump(body, { schema: HOMEASSISTANT_SCHEMA });