Updated CHANGELOG.md and intro.md

[rickecon]

This PR:

• Fixes the version comparison entry at the bottom of CHANGELOG.md for version 0.15.6
• Updates the tags in intro.md to correspond to the tags in README.md
• Updates the version to 0.15.7 in pyproject.toml and ogcore/__init__.py in order to capture the uv.lock changes from PR Bump pillow from 12.1.1 to 12.2.0 #1102 and PR Bump pytest from 9.0.2 to 9.0.3 #1103.

cc: @jdebacker

[codecov-commenter]

Codecov Report

✅ All modified and coverable lines are covered by tests.
✅ Project coverage is 72.85%. Comparing base (c24e756) to head (1b860d6).
⚠️ Report is 4 commits behind head on master.

Additional details and impacted files

@@           Coverage Diff           @@
##           master    #1104   +/-   ##
=======================================
  Coverage   72.85%   72.85%           
=======================================
  Files          21       21           
  Lines        5201     5201           
=======================================
  Hits         3789     3789           
  Misses       1412     1412           

Flag	Coverage Δ
unittests	72.85% <100.00%> (ø)

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Files with missing lines	Coverage Δ
ogcore/__init__.py	100.00% <100.00%> (ø)

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