clarified documentation for Geometry.scale

[zerothi]

It is now clearer that it scales both atomic
and lattice coordinates.

Fixes #949.

• Closes Docs for Geometry.scale is slightly misleading #949
• Added tests for new/changed functions?
• Documentation for functionality in docs/
• Changes documented in changes/<pr-num>.<type>.rst

[codecov]

Codecov Report

✅ All modified and coverable lines are covered by tests.
✅ Project coverage is 86.90%. Comparing base (3184deb) to head (58b15e1).
⚠️ Report is 2 commits behind head on main.

Additional details and impacted files

@@           Coverage Diff           @@
##             main     #950   +/-   ##
=======================================
  Coverage   86.90%   86.90%           
=======================================
  Files         412      412           
  Lines       54326    54326           
=======================================
  Hits        47214    47214           
  Misses       7112     7112           

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