Add contrib guide to the side bar

[rasika-chivate]

No description provided.

[Copilot]

Pull request overview

Adds a contributing-guide link to the documentation sidebar.

Changes:

• Adds sidebar link styling and layout.
• Adds an in-site contributing guide.
• Updates the sidebar edit template.

Reviewed changes

Copilot reviewed 3 out of 3 changed files in this pull request and generated 2 comments.

File	Description
docs/css/extra.css	Styles the sidebar contribution banner.
docs/CONTRIBUTING.md	Adds contribution instructions.
_resourcepdf/overrides/partials/edit.html	Adds the guide link beneath the edit link.

Suppressed comments (4)

docs/CONTRIBUTING.md:19

• This guide is for Percona Server for MongoDB, but this sentence names the separate Percona Distribution for MongoDB product. Correcting the product name avoids sending contributors to the wrong documentation context.

Percona Distribution for MongoDB documentation is written in [Markdown](https://www.markdownguide.org/basic-syntax/) language, so you can 

docs/CONTRIBUTING.md:20

• The fragment omits the “a” in “via”, while the heading on line 42 generates #edit-documentation-online-via-github. As written, this in-page link does not navigate to the section.

[edit it online via GitHub](#edit-documentation-online-vi-github). If you wish to have more control over the doc process, jump to how to [edit documentation locally](#edit-documentation-locally). 

docs/CONTRIBUTING.md:98

• The same sentence is repeated on consecutive lines. Remove the duplicate so the building instructions read correctly.

You can do it in these ways:

docs/CONTRIBUTING.md:103

• The misspelled fragment does not match the Repository structure heading, so this in-page link is broken.

Learn more about the documentation structure in the [Repository structure](#repository-stucture) section.

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[Copilot]

Pull request overview

Copilot reviewed 4 out of 4 changed files in this pull request and generated no new comments.

Suppressed comments (6)

docs/CONTRIBUTING.md:20

• This fragment misspells via, so it does not match the generated edit-documentation-online-via-github heading ID and the link does not navigate to the section.

[edit it online via GitHub](#edit-documentation-online-vi-github). If you wish to have more control over the doc process, jump to how to [edit documentation locally](#edit-documentation-locally). 

docs/CONTRIBUTING.md:103

• This fragment misspells structure, so it does not match the generated repository-structure heading ID and produces a broken in-page link.

Learn more about the documentation structure in the [Repository structure](#repository-stucture) section.

docs/CONTRIBUTING.md:98

• The preceding sentence is repeated verbatim, so the rendered guide contains duplicated text immediately before the build options.

You can do it in these ways:

docs/CONTRIBUTING.md:15

• The new layout places this action in the right sidebar, not next to the page title, and its visible label is “Edit this page on GitHub.” Update the instruction so contributors can find the control in the UI introduced by this PR.

2. **[Contribute to documentation yourself](#contribute-to-documentation-yourself)**. Click the **Edit this page** icon next to the page title. This link leads you to the source file of the page on GitHub. There you make changes, create a pull request that we review and add to the doc project. For details how to do it, read on.

_resourcepdf/overrides/partials/edit.html:16

• This URL bypasses the newly added rendered guide and opens the repository-root guide instead. Those files already differ: the root guide tells readers to click a Jira link at the bottom of the page, which does not exist on GitHub. Link to the built docs/CONTRIBUTING.md page so sidebar users receive the guide introduced by this PR.

      <a href="https://github.com/percona/psmdb-docs/blob/8.3/CONTRIBUTING.md"

docs/CONTRIBUTING.md:19

• The guide and site are for Percona Server for MongoDB, but this sentence names the separate Percona Distribution for MongoDB product. This gives contributors the wrong project context.

This issue also appears in the following locations of the same file:

• line 20
• line 98
• line 103

Percona Distribution for MongoDB documentation is written in [Markdown](https://www.markdownguide.org/basic-syntax/) language, so you can