refactor: Add languages list in YAML

[ianlewis]

Description:

Add configuration for languages as a YAML file.

Related Issues:

Updates #460

Checklist:

• Review the CONTRIBUTING.md documentation.
• Add a reference to a related issue in the repository.
• Add a description of the changes proposed in the pull request.
• Add unit tests if applicable.
• Add a note in the CHANGELOG.md if applicable.
• Sign the Google CLA.

[codecov]

Codecov Report

Merging #666 (4c6a24d) into main (9946b49) will decrease coverage by 0.18%.
The diff coverage is 80.76%.

Additional details and impacted files

@@            Coverage Diff             @@
##             main     #666      +/-   ##
==========================================
- Coverage   80.48%   80.30%   -0.18%     
==========================================
  Files          19       19              
  Lines        1122     1127       +5     
  Branches       14       14              
==========================================
+ Hits          903      905       +2     
- Misses        157      159       +2     
- Partials       62       63       +1     

Files Changed	Coverage Δ
internal/scanner/languages.go	76.92% <76.92%> (ø)
internal/scanner/scanner.go	76.49% <83.33%> (ø)
internal/todos/todos.go	100.00% <100.00%> (ø)