No Axis Text color option

[UVLabs]

I didn't check all charts but so far I could see that barcharts and filled line charts do not have the option.

If user tries to put a transparent chart against a dark background then there would be readability issues:
http://prntscr.com/cbix8w @selul

[selul]

@contactashish13 can you check ?

[contactashish13]

PR: https://github.com/Codeinwp/visualizer-pro/pull/31