refactor: RuneReader

[ianlewis]

Description:

Refactors the RuneReader by moving it to it's own package and removes the internal byte buffer in favor of using bufio.Reader.

Related Issues:

Fixes #441

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 #842 (8cce22e) into main (10063f2) will increase coverage by 1.28%.
The diff coverage is 82.22%.

Additional details and impacted files

@@            Coverage Diff             @@
##             main     #842      +/-   ##
==========================================
+ Coverage   80.76%   82.05%   +1.28%     
==========================================
  Files          19       19              
  Lines        1144     1120      -24     
  Branches       14       14              
==========================================
- Hits          924      919       -5     
+ Misses        158      146      -12     
+ Partials       62       55       -7     

Files	Coverage Δ
internal/utils/slice.go	100.00% <100.00%> (ø)
internal/runes/reader.go	89.47% <89.47%> (ø)
internal/scanner/scanner.go	77.70% <38.46%> (ø)