[Feature] Placeholder API Support

[razorrider7]

Describe the feature you'd like
Placeholder API support, to see if a placeholder matches another:
- 'papi{placeholder="%player_name%",operation="matches",compare="razorrider7"}' True if player's username is razorrider7
or if a placeholder is mathematically equal to (4.0 == 4 but that doesn't work for string matching):
- 'papi{placeholder="%player_level%",operation="==",compare="50"}' True if player's exp level = 50
or if a placeholder is greater than:
- 'papi{placeholder="%player_level%",operation=">",compare="50"}' True if player's exp level > 50
or if a placeholder is less than:
- 'papi{placeholder="%player_level%",operation="<",compare="50"}' True if player's exp level < 50
or if a placeholder is greater than or equal to:
- 'papi{placeholder="%player_level%",operation=">=",compare="50"}' True if player's exp level >= 50
or if a placeholder is less than or equal to:
- 'papi{placeholder="%player_level%",operation="<=",compare="50"}' True if player's exp level <= 50