Add docs for passing complex data types

[jeffcharles]

Description of the change

Adds documentation containing some code examples for using complex data types like byte arrays, strings, and structured data in Wasm functions.

Why am I making this change?

We've identified that lots of folks extending Javy struggle with how to do this so hopefully having some documentation will make it easier for them.

Checklist

• I've updated the relevant CHANGELOG files if necessary. Changes to javy-cli and javy-core do not require updating CHANGELOG files.
• I've updated the relevant crate versions if necessary. Versioning policy for library crates
• I've updated documentation including crate documentation if necessary.

[saulecabrera]

Generally looks good. It might be also useful to:

• Add, perhaps at the end of the complex-data-types-in-wasm-functions.md, that passing structured data between the host and guest could be solved at a higher level if Javy implemented support for the component model, but that we haven't gotten to it yet.
• Add some .wat examples along with all the Rust code that you've included (even if it's just the signature of the functions) with the hope of making the examples easier to understand.