add responsive ui example

[x-0D]

important change - add viewport meta into headers to make responsive work on mobile devices

<meta name="viewport" content="width=device-width, initial-scale=1, user-scalable=no">

proved to build on macos 15.0.1 m2 (arm64)

haxe: [4.3.6]
wxWidgets: [3.2.6]

haxeui-core: [1.7.0]
haxeui-flixel: [1.7.0]
haxeui-html5: [1.7.0]
haxeui-hxwidgets: [1.7.0]
hxWidgets: [1.12.0]