resize avatar icon

[tcm390]

set cameraOffset based on the avatar head size in avatar-screenshotter.js

related: https://github.com/webaverse/app/issues/2939

result: https://github.com/webaverse/app/pull/3491#issuecomment-1205832633

[tcm390]

Result

current App	Resize

[lalalune]

output looks good but @tcm390 can we rename decapitatePosition since this code isn't for decapitation?

[tcm390]

rename neckposition

output looks good but @tcm390 can we rename decapitatePosition since this code isn't for decapitation?

[tcm390]

[use bounding box to get highest point

[alisaad673]

It has improved alot for most of the vrms. Some of the vrms such as meebits still appear a bit zoomed in. But i guess its an improvement.