Export parameter keys (@W-15676813@)

[vmarta]

This PR exports the parameter keys for each API method, so that a client like commerce-sdk-react will be able to rely on them (and no longer hardcoding those param keys).

For an example on how to consume the exported parameter keys, please see SalesforceCommerceCloud/pwa-kit#1812

Note: this PR is for the parameter keys (not its Typescript types). So we're exporting the list/array.

Previous PR: #157

How to test-drive

In this case, I worked with 2 separate repos: this commerce-sdk-isomorphic (exports the parameter keys) and the pwa-kit (to consume those keys).

So first of all, let's build the commerce-sdk-isomorphic to get its minified output:

1. yarn install
2. yarn run renderTemplates
3. yarn run build:lib
4. If you need more details: https://github.com/SalesforceCommerceCloud/commerce-sdk-isomorphic/blob/export-parameter-keys/Contributing.md

Once we've gotten those minified scripts, we need to somehow use them in the pwa-kit repo. I've tried npm link but gotten an error. I'm not sure how to npm link properly within a monorepo like ours. Anyways, I manually created a symlink instead, like this:

1. Switch to the pwa-kit repo and check out this sample PR: [commerce-sdk-react] Try consuming parameter keys from isomorphic lib pwa-kit#1812
2. Create symlink from commerce-sdk-react

	# From "pwa-kit/packages/commerce-sdk-react"
	rm -r node_modules/commerce-sdk-isomorphic/lib
	ln -s ~/repos/commerce-sdk-isomorphic/lib node_modules/commerce-sdk-isomorphic

3. Now in your code editor, open the file "packages/commerce-sdk-react/src/hooks/ShopperProducts/query.ts".
4. Inspect the values of some variables, and you'll see the parameter keys like this:

[vmarta]

The latest sizes.. they're a slight increase from before.

[joeluong-sfcc]

Nice way to also include the endpoint names