render: fix sketch arrowheads

[gavin-ts]

Summary

Fixes sketch arrowheads sometimes appearing broken, and render them in a sketched style.

Details

• the sketch path isn't reliable to use markers on, causing the arrowheads to sometimes appear pointed in different directions
• this can be avoided by rendering the arrowheads separately
• adds special sketch versions of the arrowheads
• fixes sketch: Arrowheads #502
• ci had slightly different floating point values from rough js so I added code to truncate floats from rough to 6 decimal values

new arrowheads test before

after rendering arrowheads separately

after rendering sketch specific arrowheads (final)

[katwangy]

<-> and triangle arrow is the same style? i think the <-> can look more "arrow-y"

i think “crows foot one” is a lil weird. circle can be a tad bigger (to match crows foot many) and the line can be more in the middle of the circle and the edge

@gavin-ts

[alixander]

arrow is the more arrow-y one @katwangy

[alixander]

but yeah i think the example is confusing, since <-> is default triangle, it's covered twice

[gavin-ts]

updated the test example to remove the duplicate triangle case (and make the cf one circle larger and its line further away)

[gavin-ts]

moved them closer to the shape to match the positions of the non-sketched arrowheads

non-sketched arrowheads

sketched