Icons: TableIcons slow to render

[rpbouman]

Since we upgraded tabler icon font from 3.26.0 to 3.28.1 (7f29fff#diff-ce434ef5cc161194b450135a3586eb89357fc270e8aaa8e336db5a04e8d52fbeR21), inital rendering after load is slow. That is, the page loads normal but icons aren't there and suddenly appear after a couple of seconds.

The weird thing is that the tabler library gets cached and loaded from disk, so it appears that it is really the icon rendering that takes longer.

Whatever the cause, I think we should downgrade again to a version that is quicker, certainly before we do a new release.

[rpbouman]

This issue is closed for now, but only by downgrading tabler icons.

• I filed a bug with tabler: Slowdown rendering Tabler Icons using webfont starting from version 3.26 tabler/tabler-icons#1310 let's monitor that, ideally that gets picked up and we can upgrade again
• what might be a good idea anyway is to compile our own version of the font, using only the icons we actually use. https://github.com/tabler/tabler-icons#compiling-fonts. This may be interesting if it means quicker app load time, but requires investigation, as well as some sort of solution to figure out just which icons we are using. It would also mean some sort of build step.