Feature request: Adding captcha check

[kolderz]

Adding a captcha check with a custom background to prevent bypasses.

[4drian3d]

The only platform where this check could be added correctly is Paper, Velocity should still handle packets. If you require this functionality in Velocity, you could use LimboAPI, although I do not recommend its use

[kolderz]

@4drian3d I'm pretty sure most servers use Paper nowadays. Do you have any idea why the server-list-check sometimes gives a false positive check? Like a player pinged and join the server but still got blocked by the plugin. A lot of players on my server already pinged the server but still fail the check.