✨ Provide access to visualization of simulated DD in Python

[burgholzer]

Description

This PR enables Python users of our tool to get access to the Graphviz file for the simulated DD in order to inspect the final decision diagram.
This required very little code changes and should be rather convenient to use as, e.g., illustrated in the new docs section.

Checklist:

• The pull request only contains commits that are related to it.
• I have added appropriate tests and documentation.
• I have made sure that all CI jobs on GitHub pass.
• The pull request introduces no new warnings and follows the project's style guidelines.

[codecov]

Codecov Report

Merging #306 (51fb2d7) into main (44fb144) will decrease coverage by 0.1%.
The diff coverage is 93.7%.

Additional details and impacted files

@@           Coverage Diff           @@
##            main    #306     +/-   ##
=======================================
- Coverage   92.5%   92.4%   -0.1%     
=======================================
  Files         32      32             
  Lines       2528    2546     +18     
  Branches     347     348      +1     
=======================================
+ Hits        2339    2355     +16     
- Misses       189     191      +2     

Flag	Coverage Δ
cpp	94.6% <93.7%> (-0.1%)	⬇️
python	85.1% <ø> (ø)

Files	Coverage Δ
include/HybridSchrodingerFeynmanSimulator.hpp	88.8% <ø> (ø)
include/Simulator.hpp	92.6% <ø> (ø)
include/UnitarySimulator.hpp	100.0% <ø> (ø)
src/HybridSchrodingerFeynmanSimulator.cpp	97.2% <100.0%> (+<0.1%)	⬆️
src/UnitarySimulator.cpp	100.0% <100.0%> (ø)
src/Simulator.cpp	94.1% <90.0%> (-2.2%)	⬇️

... and 1 file with indirect coverage changes

[hillmich]

LGTM!

[github-actions]

Cpp-Linter Report ✔️

No problems need attention.

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