ENH: improve Function.low_pass_filter and adds docs

[Gui-FernandesBR]

Pull request type

• Code maintenance (refactoring, formatting, tests)
• ReadMe, Docs and GitHub updates

Checklist

• Docs have been reviewed and added / updated
• Lint (black rocketpy/ tests/) has passed locally
• All tests (pytest --runslow) have passed locally
• CHANGELOG.md has been updated (if relevant)

Current behavior

While using the new low_pass_filter method, I noticed some minor adjustments could be done, let's see:

New behavior

• Persist the inputs, outputs and title of the original Function
• Improve the method docstring
• Add an example to the .rst file

Breaking change

• No

[Gui-FernandesBR]

This is how the new docs look like:

[codecov]

Codecov Report

Attention: 1 lines in your changes are missing coverage. Please review.

Comparison is base (ead9219) 72.32% compared to head (7895a1e) 72.33%.

Files	Patch %	Lines
rocketpy/mathutils/function.py	0.00%	1 Missing ⚠️

Additional details and impacted files

@@             Coverage Diff             @@
##           develop     #538      +/-   ##
===========================================
+ Coverage    72.32%   72.33%   +0.01%     
===========================================
  Files           56       56              
  Lines         9389     9389              
===========================================
+ Hits          6791     6792       +1     
+ Misses        2598     2597       -1     

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