feat: Add support for looser TODO special case

[ianlewis]

Description:

Adds support for a special case of TODO comments with no whitespace between the comment start and "TODO" and with no delimiter between "TODO" and the message.

//TODO This is a todo comment.

Related Issues:

Fixes #514

Checklist:

• Review the CONTRIBUTING.md documentation.
• A reference to a related issue in the repository.
• A description of the changes proposed in the pull request.
• Please make sure to sign the Google CLA.
• Please make sure your commits include a Developer Certificate of Origin signoff.
• Please add unit tests

[codecov]

Codecov Report

Merging #537 (dbefef4) into main (5c4ac57) will increase coverage by 0.19%.
The diff coverage is 100.00%.

Additional details and impacted files

@@            Coverage Diff             @@
##             main     #537      +/-   ##
==========================================
+ Coverage   80.27%   80.46%   +0.19%     
==========================================
  Files          19       19              
  Lines        1110     1121      +11     
  Branches       14       14              
==========================================
+ Hits          891      902      +11     
  Misses        157      157              
  Partials       62       62              

Files Changed	Coverage Δ
internal/todos/todos.go	100.00% <100.00%> (ø)