Input "Form" Validation

[GlenDC]

• Make sure to allways allow empty fields, such that the user can always erase the entire field via backspace, without automatically adding a default value (this is just annoying)
  • This might mean that for things such as creating a new document we might want a new alias type, such as DocumentDescription { ... } so that we an store all it's field as Nothing.
  • Perhaps we even want a general Form type alias that can automate the entire updating and invalidating of things
• Input fields (+ label) should have an invalid state (that also show an error message)
• Disable form button when a label is invalid

[GlenDC]

Validation works, and a basic form system is implemented. Now we still need to expand the layout system:

• Input fields need to get optional error messages (with an svg icon)
• Buttons need a disable option that's visually clear
• Styling for these changes is needed as well.

This issue can probably be solved while solving #109 .