Update some SDF's to have uniform aspect ratio coordinate systems internally

[vade]

Some SDF's appear to exhibit non uniform coordinate systems (ie stretched) when stroking, resulting in uneven stroke widths

This means that stroke width using the SDF / Draw stroke function has a non uniform size depending on which axis is being stroked

(see this thread for some examples https://x.com/_vade/status/1853273734087311471?s=61)

So far I've found

• Cross
• Tri

but I suspect there may be more. I'll update this issue as I find them.

[patriciogonzalezvivo]

Reference to consider:

• https://iquilezles.org/articles/distfunctions2d/
• https://iquilezles.org/articles/distfunctions2dlinf/
• https://iquilezles.org/articles/distgradfunctions2d/