Adjust recalculated figure size based on ratio instead of difference

[Naikless]

This solves issues with pgfplots' groupplot environments that lead to negative widths/heights while iteratively searching for the correct scaling factor.

Issues this should solve:
#5
https://tex.stackexchange.com/questions/174013/scaling-multi-column-groupplot-while-maintaining-font-size-and-node-placement
https://tex.stackexchange.com/questions/605840/tikzscale-fails-for-group-plot-with-three-elements-but-works-for-two-elements
https://tex.stackexchange.com/questions/651294/tikzscale-package-not-working-with-group-plots
https://tex.stackexchange.com/questions/230974/conflict-tikzscale-and-matrix-group-plot
https://tex.stackexchange.com/questions/594924/properly-adjust-pgfplot-group-plot-to-textwidth/595722#595722
https://tex.stackexchange.com/questions/524210/create-a-groupplot-with-specific-total-width-font-family-and-font-size

I had the same issues whenever trying to scale a groupplot and now finally got around to do something about it,

[fwdekker]

Thank you for this, I was getting the same bug. I compiled your code*, put the resulting tikzscale.sty in my project, and the bug was solved :-)

* I couldn't get compilation working so I actually just took the .sty file bundled with my LaTeX installation and applied the same changes you made in this PR.

[Naikless]

Glad that the effort helped someone else, too. 😄

Bit of a bummer that this project has been abandoned quite a while ago, same as tikzplotlib.

[MagicMuscleMan]

Yes, sorry, for that, but I haven't found the motivation to work on this for years (not because this is boring, but because other projects interest me more) and it is unlikely to change soon.
But if anyone wants to take over I am open to that. That's why it's open source after all.

[Naikless]

No need to be sorry, that's just what happens with these kind of open source projects, I didn't mean it as a complaint.

I mean, my fork already exists, in the end it's just the question of which version is referenced in CTAN. Or it just needs someone here to merge potential PRs.

[fwdekker]

@MagicMuscleMan Don't worry, I know the feeling :-)