Add linking script

README.template.md

@@ -40,3 +40,50 @@ Specific imports:
 import { myFunction } from "#{REPO_NAME}#/myFunction";
 import { myObject } from "#{REPO_NAME}#/myObject";
 ```
+
+# Contributing
+
+## Testing your changes in an external app
+
+You have made some changes to the code and you want to test them
+in your app before submitting a pull request?
+
+Assuming `you/my-app` have `#{REPO_NAME}#` as a dependency.
+
+```bash
+cd ~/github
+git clone https://github.com/you/my-app
+cd my-app
+yarn
+
+cd ~/github
+git clone https://github.com/garronej/#{REPO_NAME}#
+cd #{REPO_NAME}#
+yarn
+yarn build
+yarn link-in-app my-app
+npx tsc -w
+
+# Open another terminal
+
+cd ~/github/my-app
+rm -rf node_modules/.cache
+yarn start # Or whatever my-app is using for starting the project
+```
+
+You don't have to use `~/github` as reference path. Just make sure `my-app` and `#{REPO_NAME}#`
+are in the same directory.
+
+> Note for the maintainer: You might run into issues if you do not list all your singleton dependencies in
+> `src/link-in-app.js -> singletonDependencies`. A singleton dependency is a dependency that can
+> only be present once in an App. Singleton dependencies are usually listed as peerDependencies example `react`, `@emotion/*`.
+
+## Releasing
+
+For releasing a new version on GitHub and NPM you don't need to create a tag.  
+Just update the `package.json` version number and push.
+
+For publishing a release candidate update your `package.json` with `1.3.4-rc.0` (`.1`, `.2`, ...).  
+It also work if you do it from a branch that have an open PR on main.
+
+> Make sure your have defined the `NPM_TOKEN` repository secret or NPM publishing will fail.