Button CORE

Dark mode Background

Name and description	Type	Value
`[appearance]` Appearance	`string`	`'primary'`
`[iconStart]` Icon on the left side	`string`	`''`
`[iconEnd]` Icon on the right side	`string`	`''`
`[loading]` Loading indicator (import `TuiButtonLoading` )	`boolean`
`[size]` Size	`TuiSizeXS \| TuiSizeL`	`'l'`