Docs: Enhance README.md with improved formatting and structure

[Manas-Dikshit]

This PR improves the readability and structure of the README.md file to help contributors set up their local environment and add content more efficiently. No functional code changes were made to the website itself.

Changes
Restructured Hierarchy: Organized setup and content creation steps into clear, numbered sections.
Improved Formatting: Used syntax highlighting for code blocks and tables/quotes for important links.
Visual Clarity: Added horizontal rules and consistent bolding to make the guide more "scannable" for new developers.
Clarity: Ensured all existing instructions (Hugo versions, directory paths, and SEO tips) are preserved but presented more clearly.

How to Test
Open the README.md file in a Markdown previewer or directly on the GitHub repository page.
Verify that all links to Hugo documentation and the GRASS style guide are working.
Confirm that the code snippets for config.toml and Event headers are correctly formatted.

[cwhite911]

Thank you for working on improving documentation. However, if you are using AI tooling please make sure you fact check and review the content before creating a PR. With any additional research into GRASS and the website you would have learned that the details of the PR are mostly incorrect.

Again, thank you for your contribution, please update the PR after you do some additional research.