Documentation for available emitters?

[sogaiu]

As requested, here is a request for documentation regarding the available emitters :)

[saikyun]

Added the available emitters here, and docs on the most commonly used ones. Need to write a bit about callbacks, then it should be ok.

https://github.com/Saikyun/freja/commit/3766b9ca51dab9097d3161de0e9765b1449d9adf#diff-672cb87f3f83f5a30edd82e1cf416ee5b90a1a315a9bdc6f63951ec5dcc50e5d

[sogaiu]

Thanks! I found what I read so far to be pretty clear.