feat: extend reward plot for multiple signals

[JeanElsner]

No description provided.

[codecov]

Codecov Report

Attention: Patch coverage is 75.00000% with 5 lines in your changes missing coverage. Please review.

Project coverage is 89.93%. Comparing base (cd1c01f) to head (27710fd).
Report is 2 commits behind head on main.

Files	Patch %	Lines
src/dm_robotics/panda/utils.py	73.68%	5 Missing ⚠️

Additional details and impacted files

@@            Coverage Diff             @@
##             main      #11      +/-   ##
==========================================
- Coverage   90.34%   89.93%   -0.41%     
==========================================
  Files           9        9              
  Lines         932      944      +12     
==========================================
+ Hits          842      849       +7     
- Misses         90       95       +5     

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