form to add feed with name and url and display on home scene

[pxue]

from the home screen, one can navigate to an "add feed" form from clicking on the "Add Feed" button on the navigation bar.

• Feed scene should allow user to add a new feed, with name and url as inputs, button to save the feed into the data store (no need for persistence for now)
• Display added feed on the home scene
• bonus: make sure same feed can't be added twice (unique via url?)

Things involved here:

• implement a couple text input fields on the Feed scene, get them to handle text changes.
• implement a submit button, that when clicked, it submits the "new feed"
• this function on feedStore needs to be implemented
• display the added feeds on the home screen