Add lazyComp for easy non-rerendered component

Similarly to Fable.React’s lazyView, we should have a function to easily create a component whose view function doesn’t need to be called if the model hasn’t changed. Currently this requires creating a Component class.

Proposed API mirroring Fable’s:

val lazyComp
     : viewFunction: ('model -> Node)
    -> 'model -> Node
    when 'model : equality

val lazyCompWith
     : equal: ('model -> 'model -> bool)
    -> viewFunction: ('model -> Node)
    -> 'model -> Node

val lazyComp2
     : viewFunction: ('model -> Dispatch<'msg> -> Node)
    -> 'model -> Dispatch<'msg> -> Node
    when 'model : equality

val lazyComp2With
     : equal: ('model -> 'model -> bool)
    -> viewFunction: ('model -> Dispatch<'msg> -> Node)
    -> 'model -> Dispatch<'msg> -> Node

val lazyComp3
     : viewFunction: ('model1 -> 'model2 -> Dispatch<'msg> -> Node)
    -> 'model1 -> 'model2 -> Dispatch<'msg> -> Node
    when 'model1 : equality and 'model2 : equality

val lazyComp3With
     : equal: (('model1 * 'model2) -> ('model1 * 'model2) -> bool)
    -> viewFunction: ('model1 -> 'model2 -> Dispatch<'msg> -> Node)
    -> 'model1 -> 'model2 -> Dispatch<'msg> -> Node

[Tarmil]

I was thinking we can simply have a single Component type for all lazy views, which receives the view function as a [<Parameter>]. It can even simply inherit from ElmishComponent, which already has everything needed besides this parameter.

[brikken]

@Tarmil Thank you for the feedback. I’ve made changes accordingly, added the last two signatures, added an additional example showcasing custom equality, and created a pull request with all the changes.