added example of recommendation engine (favorite t-shirts)

[LegendOfGIT]

Description

An expample of a recommendation engine, build with brain,js

Motivation and Context

Show other devs how to use brain.js in the real world

How Has This Been Tested?

Manually ;)

Types of changes

• added a folder in examples with example code for recommendation engine

Author's Checklist:

• My code focuses on the main motivation and avoids scope creep.
• My code passes current tests and adds new tests where possible.
• My code is SOLID and DRY.
• I have updated the documentation as needed.

Reviewer's Checklist:

• I kept my comments to the author positive, specific, and productive.
• I tested the code and didn't find any new problems.
• I think the motivation is good for the project.
• I think the code works to satisfies the motivation.

[freddyC]

Typically I would suggest "Let put this in a sister repo to keep brain.js small/clutter free" but I think I am changing my attitude a bit.

Also this is a super simple example, well done, and starts sets up a way to add additional simple examples.

The only thing I can think of to improve this (off the top of my head) would be to add a readme to this example's directory with a brief explanation on this example, then link that examples page on the main readme.

I would prefer the readme bit, but if you don't want to add it in I am not against this being merged as is.

[robertleeplummerjr]

good work guys!