perf(rules): optimize header-trim

[felipecrs]

Description

Optimizes header-trim rule to perform better. Comparing a string to another string is an unnecessary cost in this case.

I also replaced the switch/case with plain ifs, which are simpler.

Motivation and Context

I just happened to see the code, and noticed it could be improved.

Usage examples

N/A

How Has This Been Tested?

Existing tests pass.

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)

Checklist:

• My change requires a change to the documentation.
• I have updated the documentation accordingly.
• I have added tests to cover my changes.
• All new and existing tests passed.

[codesandbox-ci]

This pull request is automatically built and testable in CodeSandbox.

To see build info of the built libraries, click here or the icon next to each commit SHA.

[escapedcat]

Can you run yarn format-fix to get it green? Thanks

[felipecrs]

@escapedcat, done, thank you!