Add multi-source support

[hashknot]

This PR adds support for generating URLs across multiple imgix sources.

Multiple sources can be specified through the following configuration:

imgix:
  sources:  # imgix source-secure_url_token key-value pairs.
    assets.imgix.net: FACEBEEF12
    assets2.imgix.net:            # Will generate unsigned URLs
  default_source: assets.imgix.net  # (optional) specify a default source for generating URLs.

and used in the following manner:

<img src={{ "/images/bear.jpg" | imgix_url: "assets2.imgix.net", w: 400, h: 300 }} />
<img src={{ "/images/bear.jpg" | imgix_url: w: 400, h: 300 }} />

This is a completely backwards compatible change.

[jayeb]

One small grammatical fix in the README, but otherwise looks great 👍

[jayeb]

Should be "the following options"

[thexavismith]

Ran into this exact issue today! Would love to see this merged

[thexavismith]

@jayeb Will this be merged soon? I'd love to be able to have multiple sources…

[sherwinski]

Hey @smithtimmytim sorry for the very delayed response here. Multi-source support is now available via v1.2.0 🎉