docs: expand contributing.md

Author: thomcsmits

CONTRIBUTING.md

@@ -1,9 +1,49 @@
 # Contributing docs
 
+We welcome contributions!
+
+## Getting started
+
+### PNPM
+We use PNPM a package manager. To run the development server:
+
+```sh
+pnpm install
+pnpm run dev
+```
+
+The development server refreshes while editing code.
+
+### Branches
+We use the convention of `{github-username}/{descriptive-title}` for branches.
+
+### Linting 
+We use ESLint for linting. You can run the following: 
+```sh
+pnpm run lint
+```
+
+## Depending on a change in gosling.js
+If your development relies on a change in gosling.js that has not been published yet, you can create your own packaged version of any branch by running the following on the desired branch in the gosling.js repo.
+```sh
+yarn
+yarn build
+yarn pack
+```
+You can then add this .tgz file with pnpm, or refer to it as follows:
+`"gosling.js": "file:<relative path to file>"`
+
 ## Structure
 
 This project consists of three components
 
+Gosling Component is created with a spec.
+    GosRef refers to this GoslingComponent.
+    The AltGoslingComponent subscribes to specResolved and rawData from GosRef
+
+Whenever an event is published to specResolved, the AltGoslingComponent spec-map is created.
+    
+
 ### 1: Set-up of alt-text tree data from Gosling spec
 
 Input: