docs: Add documentation about errors (codespace and codes)

[ryu1-sakai]

Description

Adds documentation about errors (codespace and codes) caused by wasm.

Motivation and context

Errors (codespace and codes) are part of the interface between servers (mainnet nodes) and clients.
So their specs need to be clearly defined and described in somewhere shared by both sever and client developers, such as protocols, official documents, etc.

How has this been tested?

Confirmed that make install succeeded.

Checklist:

• I followed the contributing guidelines and code of conduct.
• I have added a relevant changelog to CHANGELOG.md
• I have added tests to cover my changes.
• I have updated the documentation accordingly.
• I have updated API documentation client/docs/swagger-ui/swagger.yaml

[loloicci]

Thank you for this work, @ryu1-sakai !
Could you write where (what part of code) these errors information comes from, if it is clear and collected in a file?

[zemyblue]

Thank you for your contribution.
Please add a link to the table of contents at the top of this x/wasm/README.md.

[ryu1-sakai]

@loloicci, the information of the documentation was taken from the following code.
https://github.com/Finschia/wasmd/blob/0a1d4576947632cf00f7dba16c564657079debe5/x/wasm/types/errors.go

@zemyblue, I added the link in the table of contents.
0faf83d

[loloicci]

@ryu1-sakai

the information of the documentation was taken from the following code.
https://github.com/Finschia/wasmd/blob/0a1d4576947632cf00f7dba16c564657079debe5/x/wasm/types/errors.go

Thank you. How about adding the info on this file path to README?

[ryu1-sakai]

@loloicci

How about adding the info on this file path to README?

I think it's beter not to mention errors.go here.

What should be written here is external specifications, not internal designs/implementations. The content added by this PR explains external specifications about errors, which both servers (nodes in case of Finschia) and clients need to know.

On the other hand, errors.go is part of internal implementations. Internal implementations may be modified as part of refactoring (without changes in external specifications) in the future. So it's better NOT to mention internal implementations in the document to avoid necessity to also modify documents when we refactor internal implementations.

[zemyblue]

LGTM

[loloicci]

OK, then now we will add error info to README, and after Finschia/finschia-sdk#942 is solved, we will unify the way to manage error info with finschia.