Add CONTRIBUTING doc

CONTRIBUTING.md

@@ -0,0 +1,43 @@
+# Contributing
+
+Thanks for your interest in contributing to Cookie Though! Please take a moment to review this document **before submitting a pull request**.
+
+## Pull requests
+
+**Please ask first before starting work on any significant new features.**
+
+It's never a fun experience to have your pull request declined after investing a lot of time and effort into a new feature. To avoid this from happening, we request that contributors create [an issue](https://github.com/inthepocket/cookie-though/issues) to first discuss any significant new features. This includes things like adding new utilities, creating new style rules, etc.
+
+## Coding standards
+
+Our code formatting rules are defined in [.eslintrc.js](https://github.com/inthepocket/cookie-though/blob/master/.eslintrc.js). You can check your code against these standards by running:
+
+```console
+npm run lint
+```
+
+To automatically fix any style violations in your code, you can run:
+
+```console
+npm run lint -- --fix
+```
+
+## Running tests
+
+You can run the test suite using the following commands:
+
+```console
+npm run test
+```
+
+Please ensure that the tests are passing when submitting a pull request. If you're adding new features to Cookie Though, please include tests. We strive to have a coverage of at least 90% on this project.
+
+## Building the app and trying your changes locally
+
+In addition to the automated tests, if you'd like to test the app locally with your own app, you run the application by running:
+
+```console
+npm run dev
+```
+
+This will create a running site in the `/dist` folder which you can view in your browser at [localhost:1234](localhost:1234).

README.md

@@ -22,4 +22,4 @@ view the documentation on how to [install](https://cookiethough.dev/installation
 
 ## Contributing
 
-If you're interesting in contributing to Cookie Though, please read our [contributing docs](https://cookiethough.dev/contributing/) **before submitting a pull request**.
+If you're interesting in contributing to Cookie Though, please read our [contribution guidelines](https://github.com/inthepocket/cookie-though/blob/master/CONTRIBUTING.md) **before submitting a pull request**.