Update wiki: CHUNK_SCREEN, tic_screen, sync, etc.

[joshgoebel]

Main f6bd43f changes:

• added a new chunk CHUNK_SCREEN to every bank
• tic_screen is a 240 x 136 x 4bpp raw buffer, you can copy it to VRAM using tic_api_sync(...)
• all the import/export commands use .png format now

Originally posted by @nesbox in #1001 (comment)

[joshgoebel]

@nesbox You can assign to me.

[joshgoebel]

Just to confirm, Screen is NOT loaded into VRAM upon boot up like many of the other data types, correct?

[joshgoebel]

@nesbox To be clear this is just the 16320 bytes of screen, not all of VRAM, right?

[nesbox]

Right :)
Sorry for the delay with the response.