Issue 8

[mattg42]

Description

Fixes #8

• Added picker to select unstable branch

There's a slight problem with it. When you select a branch from the picker it greys out as if it is disabled, even though it isn't. It looks like this is just a SwiftUI bug but I will keep my eye out for any solutions.

Type of change

• [x] New feature (non-breaking change which adds functionality)

Checklist:

• [x] My code follows the style guidelines of this project
• [x] I have performed a self-review of my own code
• [x] I have commented my code, particularly in hard-to-understand areas
• [x] I have made corresponding changes to the documentation comments
• [x] My changes generate no new warnings

[mattg42]

Wasn't working for some reason so I've tried again at #65 (I'm sure it works this time)