example: add an example using the BIP329 crate with bdk_wallet

[Musab1258]

Description

This PR adds a new example file, bip329_example.rs, that demonstrates how to manage BIP-329 wallet labels when using bdk_wallet.

This fixes issue #168 by using @praveenperera's bip329 crate rather than integrating label storage directly into the core bdk_wallet. This follows the feedback I received from @notmandatory on the issue.

The example shows how to:

• Create an in-memory bdk_wallet::Wallet.
• Load/Save labels from/to a separate JSON Lines (.jsonl) file using the bip329 crate.
• Build a lookup map to correlate wallet items (addresses, txids, outpoints) with their labels.
• Demonstrate basic addition/updating of labels in memory and saving them back to the file.
• Uses tempfile to avoid leaving artifacts after running.

Notes to the reviewers

• This example requires the keys-bip39 feature to generate the mnemonic and descriptors used.

Changelog notice

Checklists

All Submissions:

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

New Features:

• I've added tests for the new feature
• I've added docs for the new feature

Bugfixes:

• This pull request breaks the existing API
• I've added tests to reproduce the issue which are now passing
• I'm linking the issue being fixed by this PR

[coveralls]

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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