docs(wallet): provide guidance on use of ChangeSet

[ValuedMammal]

This work in progress PR is meant to expand on and clarify the documentation for bdk_wallet::ChangeSet.

fixes #9

Changelog notice

TBD

Checklists

All Submissions:

• I've signed all my commits
• I followed the contribution guidelines
• I ran cargo fmt and cargo clippy before committing

[coveralls]

Pull Request Test Coverage Report for Build 14323414626

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 86.525%

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Totals
Change from base Build 14270666930:	0.0%
Covered Lines:	7269
Relevant Lines:	8401

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💛 - Coveralls

[notmandatory]

ACK 43b6725

Thanks for the very detailed description of this critical struct.

[thunderbiscuit]

That's so awesome! Thanks a bunch. 😎