docs: add configuration docs

[tac0turtle]

Description

Closes: #7765

This pr adds some docs around the config.toml file. This is a bit of duplication but for some items it provides the use case or how it should be used. We should try to add docs around the most confusing and new items

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Author Checklist

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I have...

• included the correct type prefix in the PR title
• added ! to the type prefix if API or client breaking change
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• provided a link to the relevant issue or specification
• followed the guidelines for building modules
• included the necessary unit and integration tests
• added a changelog entry to CHANGELOG.md
• included comments for documenting Go code
• updated the relevant documentation or specification
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• confirmed the correct type prefix in the PR title
• confirmed ! in the type prefix if API or client breaking change
• confirmed all author checklist items have been addressed
• reviewed state machine logic
• reviewed API design and naming
• reviewed documentation is accurate
• reviewed tests and test coverage
• manually tested (if applicable)

[samricotta]

one small nit but lgtm

[julienrbrt]

I haven't checked if it renders properly, but lgtm!
btw could you fix this here too: #15545 (comment)

[tac0turtle]

btw could you fix this here too: #15545 (comment)

done

[likhita-809]

lgtm