Add changelog docs

[lcawl]

This PR adds a new page to the how-to guides section of the docs for the new docs-builder changelog add command.
It also adds a minimal page to the Command line interface section of the docs.

It should be merged after #2319, since it's describing some behaviour implemented there.

Generative AI disclosure

1. Did you use a generative AI (GenAI) tool to assist in creating this contribution?

• Yes
• No

2. If you answered "Yes" to the previous question, please specify the tool(s) and model(s) used (e.g., Google Gemini, OpenAI ChatGPT-4, etc.).

Tool(s) and model(s) used: Used composer-1 to create the initial content based on existing pages.

[github-actions]

🔍 Preview links for changed docs

• docs/cli/release/changelog-add.md
• docs/cli/release/index.md
• docs/contribute/changelog.md
• docs/cli/index.md
• docs/contribute/index.md

[theletterf]

Nice! Some comments.