Update readme

Author: lightness

README.md

@@ -72,4 +72,19 @@ Options:
                                                       [boolean] [default: false]
   --json            show output as prettified json    [boolean] [default: false]
   -h, --help        Show help                                          [boolean]
-```
+```
+
+## Use in your app
+
+```js
+const { grt } = require('github-repo-tools');
+
+const response = await grt({ 
+  user: 'lightness',
+  package: 'typescript',
+  yarnLock: false,
+  token: '<GITHUB_TOKEN>',
+});
+```
+
+> TODO: Add more descriptive exmaple