Add Tarjan's strongly connected components algorithm

[phyrwork]

• two test cases

https://en.wikipedia.org/wiki/Tarjan%27s_strongly_connected_components_algorithm

[phyrwork]

This is an iterative version of the algorithm, shamelessly ported from the NetworkX Python implementation. I intend to use this as a base class for an implementation of Johnson's elementary cycles algorithm - coming shortly in another PR.

[clue]

@phyrwork Thank you for filing this high-quality PR and for your patience! 👍

I'd first like to get a maintenance release out to bring this library up to date before introducing any additional algorithms. Once this is done, I'm looking forward to merging more of these algorithms, so I hope you're still interested in getting this merged then

Again thank you for your valuable contribution! I understand this long wait time can be frustrating, so rest assured I'll try to get these intermediary release out as soon as time permits (this project doesn't currently get and sponsoring, so this happens mostly in my spare free time) and will then look into this PR again in more depth! 👍

[SimonFrings]

This ticket got automatically closed after renaming the master branch to 0.9.x. We're not sure of the exact reason for this, it seems like it had nothing to do with the fact to merge this PR into the old master branch, other tickets with the same situation were left untouched.

This pull request is open for quite a while now and didn't receive any updates since, this is why I suggest we leave this closed for now. If this topic is still relevant and needs some further investigation, we can always reopen it in the future and take another look 👍