Restructure the README for readability

[hussainweb]

We should update the README for better readability and also introduce more documentation relevant to contrib tracker. This a meta-issue and we should create more issues and PRs for specific tasks.

• Make the documentation available in the IDP
• Document how to use npm to build the theme within DDEV #356

Add more to the above list as we identify more specific issues.

@Yemaneberhan-Lemma, let's work on identifying the document structure here. cc @gauravaxl