Add custom prototype initialization

[rickvanveen]

Is your feature request related to a problem? Please describe.
There is currently no way to change how the prototypes are initialized or a way to provide a custom initial value for the prototypes.

Describe the solution you'd like
Add a way to accept custom prototypes.

Describe alternatives you've considered
Add multiple ways to initialize prototypes and similar to the rest of the design of skvlq, a more dynamic way to add initialization functions.

Additional context
N/a