Add an admin addborder command to permanently increase the border

[SeptyIsHere]

Description

Is your feature request related to a problem?

No

Describe the solution you'd like us to implement.

To add a command /boxed addborder 1 that command will add one more block (will have the same effect as completing an advancement)

Describe alternatives you've considered.

Giving custom advancements that are impossible? BUt that's too hard and it's not possible to make it infinite (Like to do shops for this)

Additional context

[BONNe]

Border size depends on island protection range.
You already can increase it with a command:
[admin_cmd] range add|set|reduce <player> <number>

[tastybento]

However, there is a calculation that is done now when the player logs in that will reset the protection range back to what the advancement calculation says. So, to enable this will require an additional command.