RegionGuard

New commands and flags.

• Added the merge command, use it like this: /reguard merge [number of region to merge, for example: 2] [1st region name] [second region name] [the new, merged region name]
• Added a menu command, that adds an interface for managing the selected region. Usage: /reguard menu [region]
• Added a select command, that outlines the current selected region. Usage: /reguard select [region]

First version, may or may not work on the version selected. Tested on 1.21.8.