Add modal component

[GuessWhoSamFoo]

What this PR does / why we need it:
This PR adds a modal component. It is intended to handle three cases:

1. Display some content in a modal
2. Display a form
3. Display content and a form

If the modal does not contain a form, the only button available is Close (the modal is always closable in all cases). If a form is added to the modal component, the buttons are Submit and Cancel where submit validates the form before sending a message with action.

A modal can be opened via a button or programatically though modifying the modal config as open.

Example with a stepper in a modal to be opened via table with buttonGroup:

Code sample:

fft := component.NewFormFieldText("textFormLabel", "textFormName", "")
fft.AddValidator("placeholder", "this is an error", []string{"required"})

form := component.Form{
    Fields: []component.FormField{
        fft,
    },
}

stepper := component.NewStepper("stepper", "test")
stepper.AddStep("Step1", form, "title1", "description1")
stepper.AddStep("Step2", form, "title2", "description2")

modal := component.NewModal(component.TitleFromString("Modal example"))
modal.SetBody(stepper)
modal.SetSize(component.ModalSizeLarge)

button := component.NewButton("Click me", action.Payload{}, component.WithModal(modal))


table := component.NewTable("test", "test", []component.TableCol{})
table.Config.ButtonGroup = component.NewButtonGroup()
table.Config.ButtonGroup.AddButton(button)

[mklanjsek]

This is very cool! My only comment is that it would be good to add more storybook stories to illustrate modal opening and closing as well as interactivity inside the modal.

[GuessWhoSamFoo]

Rebased to be using angular 10 and added a form example/

[wwitzel3]

I think this is fine for now. I'm still a little not sure about the magical button behavior, but I think we can iterate on that and it isn't a blocker for this PR.