Adding the ability to use %jobxp%, %jobmaxxp% etc within PlaceholderAPI

[Cleonzs]

Description of new idea or improvement on existing one
I would like to be able to use certain placeholders within PlaceholderAPI.

Detailed information what should do
As an example, I would like it if I could simplify/modify the bossbar when you are working towards a new level for a job. Right now, both strings under %jobxp% and %jobmaxxp% can be incredibly long based on how long of numbers there are. If I could use the Math expansion of PlaceholderAPI on these placeholders, I could simplify it down to a percentage value, which would save a lot of space on the bossbar and also add for a more readable, simple way to know how far you have progressed in your level.

Changing a line like this:
%joblevel% %jobname%: %jobxp%/%jobmaxxp% xp%gain%
To something like this:
%joblevel% %jobname%: %math:{jobxp}/{jobmaxxp}% Completed xp%gain%