Add GNU General Public License v2

[jeffpaul]

Added the GNU General Public License version 2 to the project. We reference GPLv2+ across the repo, but were missing the actual license file; this PR adds that in.

[github-actions]

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Co-authored-by: jeffpaul <jeffpaul@git.wordpress.org>
Co-authored-by: JasonTheAdams <jason_the_adams@git.wordpress.org>
Co-authored-by: swissspidy <swissspidy@git.wordpress.org>

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[Copilot]

Pull request overview

This PR adds the GNU General Public License version 2 (GPLv2) license file to the project. The project already references GPLv2+ in multiple places (composer.json, mcp-adapter.php, and CONTRIBUTING.md) but was missing the actual full license text file. This addition ensures proper licensing documentation for the project.

• Adds the complete and official GPLv2 license text as LICENSE.md

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[codecov]

Codecov Report

✅ All modified and coverable lines are covered by tests.
✅ Project coverage is 81.46%. Comparing base (e436fd3) to head (99593bb).
⚠️ Report is 2 commits behind head on trunk.

Additional details and impacted files

@@            Coverage Diff            @@
##              trunk      #97   +/-   ##
=========================================
  Coverage     81.46%   81.46%           
  Complexity      917      917           
=========================================
  Files            48       48           
  Lines          3162     3162           
=========================================
  Hits           2576     2576           
  Misses          586      586           

Flag	Coverage Δ
unit	81.46% <ø> (ø)

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