Add functionality for hiding handles that aren't selected

[lavenderdotpet]

coming from inkscape there should be a way to have the vertices not show up unless selected also with complex svg files is hard to read whats going on with everything fully expanded

https://github.com/MewPurPur/GodSVG/assets/51702517/c0becf22-c7fc-413f-b780-f96f18fd51d8

inkscape for comparison

https://github.com/MewPurPur/GodSVG/assets/51702517/2cde36b1-9af1-4e41-b0b0-bf9e977df39d

the svg file if wanted for testing ^