[ps2]

The dev version of #2602 and #2603: replaces the README's original Loop 1/2-era screenshots with captures of the current dev app, and refreshes the text.

Screenshots

• Phone: status screen, carb entry, meal bolus, custom presets, Lock Screen Live Activity, and the CGM picker.
• Apple Watch: main screen, carb entry, and bolus.
• Taken on a simulator pair with the simulator CGM and pump.
• The notification, complication and watch menu screenshots are dropped.
• Phone images are half resolution, and the lock screen is a JPEG (about 1 MB in total).

Text

• The app icon at a fixed size (256 px with a rounded mask, shown at 128).
• A plain description of what Loop does, with a link to LoopWorkspace.
• Features and Supported devices sections that list only what dev has; the device list is worded from the in-app pickers.
• The experimental / not-approved notice is unchanged.
• The dead Travis badge is removed.

Preview: https://github.com/LoopKit/Loop/blob/docs/readme-refresh-dev/README.md