docs: add the description of versioning rule

[da1suk8]

Description

Added the description of versioning rule.

Types of changes

• Bug fix (changes which fixes an issue)
• New feature (changes which adds functionality)
• Breaking change (fix or feature that would cause existing functionality to not work as expected)
• ETC (build, ci, docs, perf, refactor, style, test)

Checklist

• I followed the contributing guidelines.
• I have updated the documentation accordingly.
• I have added tests to cover my changes.
• The PR title and commits are followed conventional commit form.

[zemyblue]

Please add changelog

[da1suk8]

@zemyblue

In cosmwasm, CHANGELOG is generated automatically and does not need to be added.

[zemyblue]

@zemyblue

In cosmwasm, CHANGELOG is generated automatically and does not need to be added.

If then, what's this?
https:/Finschia/cosmwasm/blob/main/CHANGELOG.md

These changes are written automatically?

[da1suk8]

@zemyblue

This is used to create the CHANGELOG.

However, it does not seem to have been updated since 0.16.3-0.5.1, so will create another PR with CHANGELOG updated.