Link to docs contribution and text formatting guidelines

[valeriahhdez]

Expand on the documentation contribution workflows and conventions.

Document instructions to style text and to use Markdown tags in JSON Schema documentation.

What kind of change does this PR introduce?
It adds information on how to contribute to the JSON Schema documentation to the Improving documentation section

Issue Number:

• Closes [📝 Docs]: Update improving documentation section of contributing guide #830

Screenshots/videos:

If relevant, did you update the documentation?

Summary

This update explicitly states the two types of contributions to documentation: working on existing issues and proposing modifications.

Does this PR introduce a breaking change?

No

[benjagm]

I think it would be a good idea to create a style guide to provide some consistency about tone, structure and other resources. For example:
https://docs.medusajs.com/contribution/docs

You can place inside the docs folder like we did with the blog guidelines.

And please, remember we have this page (unused for now) with a guide on how to write markdown. https://json-schema.org/md-style-guide

I think we should create a style guide and see how we integrate this page.

[valeriahhdez]

I added a new commit that directs people to the new contribution and style guides for documentation.

PR #982 contains the changes I'm proposing to set clear documentation contribution processes and create consistent documentation for JSON Schema.