Add single year parameter flag to pontos-update-header

[llugin]

What

Add single_year flag to pontos-update-header that skips updating headers with additional modified year (YYYY-YYYY) and retains only creation year.

Why

To be able to use the tool and adhering to internal requirements (that discourage using from-to years), which makes licenses easier to maintain.

[github-actions]

Conventional Commits Report

Type	Number
Added	1

🚀 Conventional commits found.

[codecov]

Codecov Report

Attention: Patch coverage is 94.73684% with 2 lines in your changes missing coverage. Please review.

Project coverage is 90.37%. Comparing base (4fdbe3d) to head (df21d08).

Files	Patch %	Lines
pontos/updateheader/updateheader.py	94.59%	1 Missing and 1 partial ⚠️

Additional details and impacted files

@@           Coverage Diff           @@
##             main    #1021   +/-   ##
=======================================
  Coverage   90.37%   90.37%           
=======================================
  Files         103      103           
  Lines        6960     6981   +21     
  Branches      986      990    +4     
=======================================
+ Hits         6290     6309   +19     
- Misses        471      472    +1     
- Partials      199      200    +1     

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[y0urself]

Hello Leszek. Thank you for your contribution!

I wonder if it would make sense to implement the ability to revert the from-to copyright statement, if the single-year argument is passed? It would probably improve the continuity in a single repository to have either single-year or from-to copyright header format.

[llugin]

As suggested, added the feature to change existing multi-year license headers into single-year ones.