Make the scale-rotate tool's commit behavior more consistent with that of other tools

[ethanjli]

Fixes:

• Change the transformation matrix to be equal to a matrix constructed by right-multiplying a scaling matrix with a rotation matrix (see here for a visual representation), so that scaling and rotation parameters can be adjusted simultaneously between commits

Additions/changes:

• Remove the behavior to automatically commit changes in the scale/rotate tool on blur/mouseup/enter events, and instead commit changes only from a new "Commit" button
• Add a reset button for each slider in the tool. The other tools have easy reset, because their sliders can just be dragged all the way to the left. For the scale-rotate tool, the reset positions are in the middle of the sliders - so reset buttons help with usability.
• Add two more tools to the Selection Rotate and Scale Mod, flipX and flipY, which allow mirroring the selection in the x-axis or the y-axis, respectively
• Bump the script's version number from 0.4 to 0.5.1

[ethanjli]

At least a few members of LRAC (including myself) have been using this modification regularly over the past 3 weeks, and I haven't heard any issues yet, so I'm marking this PR as ready for review. Please let me know if there's anything I can do, or if you need any information from me, to make it easy to review this PR!

[conundrumer]

Given that this will exist in EmergentStudios/linerider-userscript-mods, the download URL should continue to point here, right?

[ethanjli]

Yes, when I committed 71a3b35 I wasn't sure if this repo was still going to be maintained, or if I should start an actual fork. I'll change the download URL back when I also merge ethanjli#2 into this PR.

[ethanjli]

Ok, I've reverted the download URL and merged ethanjli#2 into this PR - please let me know if there's anything else I should do on this PR!