Doc: Restructure contribution docs into the Canonical contribution model

[akcano]

No description provided.

[Copilot]

Pull request overview

This PR restructures Workshop’s contribution documentation into a Canonical-style contribution model by splitting the previous single contributing guide into focused pages (development, documentation, maintenance) and updating navigation and references across the docs and repo guidance.

Changes:

• Replaces the monolithic docs/contributing.rst content with a high-level entry point plus a hidden toctree to new contribution sub-guides.
• Adds new contribution guides for development, documentation, and maintenance, and wires them into the docs home page.
• Updates repository guidance to point at the new locations (PR template, Copilot instructions, and the code-review agent prompt), plus a spelling wordlist update.

Reviewed changes

Copilot reviewed 10 out of 10 changed files in this pull request and generated 3 comments.

Show a summary per file

File	Description
docs/index.rst	Updates site navigation and “Get involved” links to the new contribution docs structure.
docs/contributing/maintenance.rst	Adds a maintainer-focused guide (release process, CI/CD, doc tooling).
docs/contributing/documentation.rst	Adds a documentation contribution guide (setup, write, test, review).
docs/contributing/development.rst	Adds a development contribution guide (setup, test, review workflow).
docs/contributing.rst	Replaces the prior long-form guide with a concise landing page and toctree to the new guides.
docs/coding-style-guide.md	Updates references so style guidance no longer depends on removed contributing content.
docs/.custom_wordlist.txt	Adds “subshell” to the project wordlist for docs/spell checks.
.github/pull_request_template.md	Updates the template link to point at the coding style guide for error-message guidance.
.github/copilot-instructions.md	Updates pointers from the old contributing guide to the coding style guide / new contribution docs.
.github/agents/code-review.agent.md	Updates the agent’s referenced inputs to include the new contribution docs.