Form error state for material thickness

[iammikecohen]

If I opened a PR would you consider this change:

When a material thickness greater than the height of the bit is entered display an error rather than changing the material thickness to the bit height.

It should be obvious that you can’t cut a material thicker than your bit. However, I wasn’t thinking and didn’t see the form update. I can imagine others running into the same problem.

My proposed change would disable the SVG download buttons and display error text under the material thickness form field.

[bieber]

Yeah, that sounds great. If you want to send something over I'd be glad to take a look