Content migration - create "Submit to Plugin Library" article in the docs

[amberleyromo]

Issue Context

This issue is part of the content migration project (#8103), which is meant to take existing content and repurpose it so it's easier to find in the docs.

Motivation

We are doing this because many people have written excellent content that we want to canonize and maintain so more people can find it and benefit from it.

Steps to resolve this issue

Review the Gatsby docs approach

• Read the Style Guide and follow it in order for your PR to be accepted. Pay special attention to the templates.
  • Style Guide: https://www.gatsbyjs.org/docs/gatsby-style-guide/
  • Docs Templates: https://www.gatsbyjs.org/docs/templates/

Draft the doc

• Create a new file named submit-to-plugin-library.md in the docs source directory.
• Begin the newly-created markdown file with the following frontmatter:

---
title: Submit to Plugin Library
---

• Use the text of this section of the "Plugin Authoring" doc: https://www.gatsbyjs.org/docs/plugin-authoring/#publishing-a-plugin-to-the-library
• Change the section of the "Plugin Authoring" doc to link to the new page (so the content isn't duplicated, it's moved over)
• Change this section of the Source Plugin Tutorial to link to the new page, instead of the "Plugin Authoring" doc.

Add the page to the sidebar

• Add the new page to the sidebar under "Submit to Starter Library"

- title: Submit to Plugin Library
  link: /docs/submit-to-plugin-library/

Open a pull request

• Open a pull request with your work. In the PR description, include the words "closes Content migration - create "Submit to Plugin Library" article in the docs #8843"

[avneetreen]

Hey! Can I work on this ?

[avneetreen]

I attempted to work on this and created a pull request for this issue here: #8862 , please let me know if changes are required . Thanks.