Demos for flixel 5.4.0 features

[Geokureli]

We need new demos for

• FlxAseAtlasUtils - FlxAsepriteUtils demo flixel-demos#326
• Multi-Atlas
• FlxAnimationController.timeScale

[Vortex2Oblivion]

I feel like it would be a good idea to replace the demos compiled to flash with html5 versions as well.

[Geokureli]

I feel like it would be a good idea to replace the demos compiled to flash with html5 versions as well.

HaxeFlixel/flixel-demos#287
Any demos other than the ones listed here? If so, be sure to mention them in this thread

Note: for demos like FlxBlur i just removed them from the web page, things like this were rarely used, and are probably easier to recreate in html5 once the rendering backend is revamped

[MondayHopscotch]

Is the FlxAseAtlasUtils demo request just a demo showing off the features contained in FlxAsepriteUtils? I was thinking I'll try building this out.

Update: I've created a draft PR for this demo while I work on it to allow for feedback as I'm putting things into it: HaxeFlixel/flixel-demos#326