Implemented mising blending filters

[Shiwank19]

I have researched missing blending filter formulae and implemented them.Please have a look.

[abhikpal]

The code looks okay to me. But before I test things out, I have comments:

1. Could you do a merge request against the develop branch?
2. It would be nice to have some examples to go with the code. Add them here: (https://github.com/p5py/p5-examples). I usually use the following convention with examples:
   1. if it's from the examples section from Processing (Java) (https://processing.org/examples/) then it goes in the folder with the appropriate section name (so basics/math/additive_wave.py is a port of https://processing.org/examples/additivewave.html)
   2. If it's from the reference section, it goes in the reference folder (with a similar folder structure as (i))

[Shiwank19]

ok I am working on both the points you mentioned.
Sir My code is related to image directory inside examples.I am going to add examples for each blend mode.

[Shiwank19]

I have made pull request to develop branch of p5py and also added new examples for each blending mode I've implemented.I have created a pull request to develop branch of p5-examples.
Please review it.