Create base configuration modal for "Remote Web Application" widget

• Type: Task
• Status: Closed
• Priority: Minor
• Resolution: Discarded
• Affects Version/s: None
• Fix Version/s: None
• Component/s: JS APIs and Utilities
• Labels: None
• Epic/Theme:
  • FI_Developer_Experience
• Epic Link: fi-remote-web-app-widget

As described in the research document, under "Backend needs → Functional requirements → High-level":

https://docs.google.com/document/d/1L3AXKG4k229lN0w-IA0EWzOy-dflSUnGjuv-1E1w2cA/edit

We are going to need a configuration modal on the widget. The "blinking light demo" and the purpose of this ticket is just to get the modal in place with a minimal set of fields (possibly even just remote URL — note that it is not even necessary to persist this setting in this initial cut; I just want to see a UI rendered where we can put settings in further iterations), which we will then wire up and extend in subsequent tickets as we implement the OAuth-based installation flow.

Will need some design input on what the dialog should look like, but that can come after the list of options and other details about the authorization flow are finalized.