Cart abstraction

[wizardlyhel]

Create a cart abstraction with Remix mindset:

• All queries are working, still need to add cart note and select delivery mutations
• Had some trouble putting the <CartForm> component with @shopify/hydrogen

HOW to test your changes?

Post-merge steps

Checklist

• I've read the Contributing Guidelines
• I've considered possible cross-platform impacts (Mac, Linux, Windows)
• I've added a changeset if this PR contains user-facing or noteworthy changes
• I've added tests to cover my changes
• I've added or updated the documentation

[benjaminsehl]

Just reviewing some old issues and wanted to tag this one on this PR for us to consider: #113

Not necessary to solve for at this moment but worth us revisiting as we go through build @mynameisadamf