Document Uri with parse/version/sender example

[Mshehu5]

This PR address some issues in https://github.com/payjoin/rust-payjoin/issues/865 mainly this issue :

Document the Uri top level type alias and struct documentation for the individual fields exists but this assumes the reader is familiar with the Extras pattern of bitcoin_uri it should have an example of parsing a URI checking the version, and initializing sender state machine

consulted GPT codex for example

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• [x] I have disclosed my use of AI in the body of this PR.
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[coveralls]

Pull Request Test Coverage Report for Build 18942206385

Details

• 0 of 0 changed or added relevant lines in 0 files are covered.
• No unchanged relevant lines lost coverage.
• Overall coverage remained the same at 83.578%

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Totals
Change from base Build 18915517369:	0.0%
Covered Lines:	8988
Relevant Lines:	10754

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💛 - Coveralls