feat(docs): variable integer serialization types

[novusnota]

Slowly getting back in the saddle.

Issue

Closes #1252.

Checklist

• I have updated CHANGELOG.md
• I have run the linter, formatter and spellchecker
• I did not do unrelated and/or undiscussed refactorings

[anton-trunov]

The map page should also mention which annotations are supported for key and value types:

Since TVM natively supports only maps with fixed-width keys, you can only use the uint and int serialization annotations for map keys...

See #1275

[novusnota]

The map page should also mention which annotations are supported for key and value types

Got it

[anton-trunov]

@novusnota ping