v0.2.2

added sort and reverse options to shopify.products
- the default value for sort is BEST_SELLING
added filters option to shopify.products_in_collection
- previously, these collection queries had filter available: true hard-coded
- now we want to be able to display sold-out items on purpose
- so, we've changed the default behavior -- now, sold-out items will be returned in collection queries
- we've added filters option, where you can supply shopify graphql filters, currently, only specifying available is supported
- to return only in-stock products, provide filters: [{available: true}]
- to return only out-of-stock products, provide filters: [{available: false}]
- to return all the products, provide filters: [] or filters: [{}]

v0.2.0

(!) tweaked shopify.specific_products return type
- used to be Promise<GqlProduct[]>
- now is Promise<(GqlProduct | null)[]>
shopify.checkout now silently discards items with zero quantity

(!) rework pagination
- our generators no longer use return statements
- instead, all values are supplied via yield
- this fixes a bug with for await loops -- for loops ignore returned data
- this means we cannot use native done as a signal for the end of the data (when done is true, the value is discarded by for loops)
- so we've implemented our own PageReport<N> type and PageGenerator<N> type
```
const {value, done} = await page_generator.next()
const [nodes, more] = value!
```
  - now we rely on our own more instead of done to indicate that no more nodes are available
(!) rename ShepherdError to ShopifyShepherdError
(!) change Shopify constructor signature to use an options object
(!) make various Gql types optional, like variant.image, product.featuredImage, etc
add shopify.checkout({line_items: []})
add shopify.specific_products({ids: []})
i reorganized the directories and files a lot, but i don't think there are any breaking changes
added Shopify.first helper for getting only the first page
add shopify.product() for getting info on a single product
add ShopifyNotFoundError