[Suggestion] Additional requirements

[JohnS19]

Is your feature request related to a problem? Please describe.
Yes, the plugin provides limited requirements for rankups.

Describe the solution you'd like
I would like to set more requirements than the ones provided.

Describe alternatives you've considered
N/A

Additional context
Would it be possible to make placeholder conditional requirements? Such as using placeholderapi and comparing the value from that to a preset value? I've seen some spigot rankup plugins do this and it would make the plugin very flexible.

ex.
placeholder-needed=%plugin_stats_for_player%>=10

%placeholder% string. Operation can be any of: =, <, >, <=, >=, ==