docs: add documentation for BFS (#56)

[MichaeINeumann]

Hello, I made the documentation for BFS.
Please Check the ## Syntax section. I understood not exactly what I did here.
Also I'm not sure with the content at ### BFS is particularly useful for: , because I not used this algorithms in praxis.
I have only experience with dijkstra in robot programming.

[github-actions]

Hi there! Thank you for creating your first pull-request on the Graaf library :)

[codecov]

Codecov Report

Patch coverage has no change and project coverage change: -0.07% ⚠️

Comparison is base (0844d8b) 99.73% compared to head (3c4b0f7) 99.67%.
Report is 5 commits behind head on main.

Additional details and impacted files

@@            Coverage Diff             @@
##             main      #73      +/-   ##
==========================================
- Coverage   99.73%   99.67%   -0.07%     
==========================================
  Files          23       23              
  Lines        1140     1226      +86     
==========================================
+ Hits         1137     1222      +85     
- Misses          3        4       +1     

see 2 files with indirect coverage changes

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[bobluppes]

Thanks for your contribution 🚀
It looks very detailed, I will take a closer look tomorrow. Tagging #56

[bobluppes]

Hi @MichaeINeumann thank you for the contribution! The section looks very detailed and provides very good examples of BFS use cases.

Only one comment on the Syntax section, let me know what you think and we can merge it 🚀

[bobluppes]

Thanks, LGTM 👍🏻