test(changelog): add cases for docs: prefix

[beeb]

Description

This PR adds test cases for the docs: prefix.

Motivation and Context

The current test suite doesn't test the docs: prefix which is the recommended value for documentation commits for conventional commits. This change adds the relevant test cases.

Closes #164

How Has This Been Tested?

Test cases that were referring doc: were duplicated with docs: instead.

Types of Changes

• Bug fix (non-breaking change which fixes an issue)
• New feature (non-breaking change which adds functionality)
• Breaking change (fix or feature that would cause existing functionality to change)
• Documentation (no code change)
• Refactor (refactoring production code)
• Other: tests

Checklist:

• My code follows the code style of this project.
• I have updated the documentation accordingly.
• I have formatted the code with rustfmt.
• I checked the lints with clippy.
• I have added tests to cover my changes.
• All new and existing tests passed.

[orhun]

Thank you for your contribution @beeb! 🐻 Can you go to #165 and pre-empt your opinion before this PR is merged?

[welcome]

Congrats on merging your first pull request! ⛰️