feature suggestion: {.noredraw.} pragma

[choltreppe]

There is currently no easy way to surpress redraw just for one specific handler (probably because it isnt needed very often).

You can kxi.surpressRedraw = true inside your handler, but then there is no way to set it back afterwards.
The only way currently is using addEventListener manually, which isnt very elegant.

So I added addEventHandlerNoRedraw procs to karax.nim and the .noredraw. pragma to the dsl syntax.
Now you just need to do:

buildHtml(..):
...
  proc onclick {.noredraw.} =
    dostuff
...

or

proc onclick(e: Event, n: VNode) {.noredraw.} =
  dostuff

maybe this would be nice to have in the repo

[Araq]

Remove the debugEcho calls and move the logic to a helper proc.

[geotre]

You can kxi.surpressRedraw = true inside your handler, but then there is no way to set it back afterwards.

I've definitely used surpressRedraw in at least one of my projects without manually adding event handlers, I just have to figure out where

I do like this PR though, it seems less error prone than the global flag. Good work @choltreppe