Dead Simple Implementation would be to do a frame per render tick.
Overwise:

• Need to Update Atlas Sprite with animation frame
• Can we detect a loop point in a GIF Sequence
• UI
• Change GIF Length
• Looping
• Real Time / FPS
• GIF Library

GIF Item Rendering
Renders X frames then keeps rendering (up to 5 Seconds) till it finds a frame which is the same as the initial.
Realtime not currently implemented.
Using a fixed FPS of 20 as this aligns nicely with standard Atlas updates.
Looping is currently automatic.
Above gif generated with testing command: /render hand 256 animated 2

• render - Base Command
• hand - Item Source
• 256 - Render Size
• animated - Animate Render
• 2 - Frame Count (Needs to be 2+ for auto loop end to work otherwise we get a single image)