Add `.gantt_noselect` Shadow DOM

[scrodde]

Add ".gantt_noselect" too $root instead of document.body to make grid column resize work in Shadow DOM.

The codebase has different ways of toggling .gantt_noselect class. Please streamline them all to use $root instead of document.body to make this work in the shadow dom.

Examples from codebase:

✅ gantt3.$root.classList.add("gantt_noselect");
👎 ❌ document.body.className += " gantt_noselect";

[gearcoded]

@scrodde,
I think resizing should work correctly when Gantt is inside ShadowDOM.
Here is an example:
https://snippet.dhtmlx.com/ags77z42

If there are some issues, it is hard to suggest what might be wrong as I don't see your code.
In that case, please add your configuration to the following snippet and make sure that the issue is reproduced there:
https://snippet.dhtmlx.com/40tsh9uz
Then, click on the Save button and send me the link.
Or send me a ready demo with all the necessary JavaScript and CSS files so that I can reproduce the issue locally.