Feature/collections and product list

[gil--]

Beginning logic for collections pages. Super basic but starting the skeleton:

• Gatsby Node logic to create (atm, first 250 collections)
  • will need to adjust to do ALL collections for large stores
• Created Collection template
• Created ProductBox component
• Created ProductList component
  • should be useful for all instances of product boxes (related products, upsell, xsell, collections, featured products, etc.)

TODO

• Add pagination (Only first 20 products atm. We need to add collection pages for ALL products)
  • In the future, for stores with hundreds and thousands of products in a collection, we may want to offload loading those products to Apollo? Depending on build times
• I'd like to add some Jest/Enzyme test cases for the new components going forward. Would be easier to test for regressions.
• Also I need to add StoryBook so I can begin to spin up a basic style guide of reusable components...

[gil--]

Added some very basic grid styling so it's not a long list

[gil--]

Merging due to success of Netlify check. (Will add unit tests down the road which will require pass.