XCM Documentation

[franciscoaguirre]

One of the main reasons XCM is regarded as hard is the lack of documentation.
Some simple transfers we have been able to put as extrinsics in pallet-xcm people can use very easily, but as we're moving more and more towards palletXcm.execute we need good documentation to teach developers to craft xcms and use the tools surrounding it.
The XCMv5 release, which removes a lot of barriers of usage, will have a much bigger impact if it comes with the appropriate documentation.

We already have a good place to put documentation on how to configure your parachain for XCM in the rust docs, which we should keep on expanding.
We also have some documentation in the polkadot wiki which, while good, is more of a reference.
We need a place for app development docs. How to interact with a chain via XCM.
These docs should have:

• How to interact with the chain with PAPI and SubXt
• Snippets for multiple different scenarios
• How to use Chopsticks to debug xcms
• Be available for different versions (V4, V5)
• Possibly more