docs: Add contributing guide

.npmignore

@@ -1,6 +1,8 @@
 _internal
 ./.eslintrc
 ./.nvmrc
+./.prettierignore
+./.prettierrc
+CHANGELOG.md
 commitlint.config.js
-/docs
-/website
+CONTRIBUTING.md

CONTRIBUTING.md

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+# Contributing to rSR
+Follow the guide below if you'd like to get rSR running locally to start contributing.
+
+## Repository Setup
+1. Clone this repository.
+1. Run `cd rsr` to change into this repo's directory.
+1. Run `npm link` to create a symlink on your system.
+
+You will now be able to create a project locally and have access to the rSR CLI in that project. Follow the steps below to create a new local project and test your local copy of rSR out on it.
+
+## Local Project Testing Setup
+1. Create a new project and `cd` into its directory.
+1. Run `npm link @reintroducing/rsr` in your new project directory.
+1. Run `rsr -e contrib` to download all the necessary dependencies so that your project can run effectively and you can test any rSR command.
+1. Run `rsr` to initialize a new project and scaffold the files.
+
+You can now run other commands like `rsr -e start` and `rsr -e build` to see what happens to your project based on any edits you make to the rSR source code.