Added asset filter

[jaxwilko]

This PR adds an asset filter to twig.

{{ 'path/to/asset.png' | asset }}
// this is the equivilant to the blade
{{ asset('path/to/asset.png') }}

[jaxwilko]

Note: This PR now additionally includes mirroring system filters as functions

This change introduces the following functionality within twig templates:

• app - {{ 'path/to/link' | app }} or {{ app('path/to/link') }}
• media - {{ 'path/to/file.png' | media }} or {{ media('path/to/file.png') }}
• asset - {{ 'path/to/file.png' | asset }} or {{ asset('path/to/file.png') }}
• resize - {{ 'path/to/file.png' | resize }} or {{ resize('path/to/file.png') }}
• imageWidth - {{ 'path/to/file.png' | imageWidth }} or {{ imageWidth('path/to/file.png') }}
• imageHeight - {{ 'path/to/file.png' | imageHeight }} or {{ imageHeight('path/to/file.png') }}