docs: add info on how it works + (perhaps too thorough?) info on the potential issues

[kiprasmel]

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[kiprasmel]

oh shit i just realized we can avoid the issue if we implement our own --continue damn this rocks

[kiprasmel]

re-opening since i've realized that our own --continue doesn't make much sense (i don't use it / forget to use it myself, so why bother).

though, the issue mentioned in the bottom, is less of an issue now. since feat/custom-post-rewrite-game-changer, we're able to store the --amends as well, so we're able to recover better.
the multiple rebases (non-stacked) are still being worked on there, but i'll figure it out eventually i'd hope.