`screenshot_mom_official` command for map submission

[tsa96]

Add a custom command for taking screenshots exactly how we want them. Should be

• 2560x1440
• PNG
• HUD disabled (png command already does this)
• Default brightness
• High graphics settings (if this isn't too bad to change)

Then write it out to the screenshots directory with <current_map_name>_somenumbers_official

Dunno exactly where we'll implement this but we really want to enforce consistent screenshots, so this seems better than telling people the png command. ESPECIALLY because we can force default brightness, meaning if a mapper has made a really dark map on a high brightness setting, their screenshot won't like as intended. Ha!