Allow the use of load functions in the main yuck files

[FilipeTiago]

Allow the use off load function sutch as: (load "modules/workspaces/widget.yuck")
This to allow to split the main widget from the components, allows to reuse components in other widgets.

Currently if I try that it does not recognize load and it's invalid.

Also I like this modular approach because scripts / css that belong to a specific module are in that module folder. That's how I set up my waybar that I would like to replace.