Add support for embedded languages

[charlespwd]

In this PR

• Add support for other languages inside <script> and <style> tags

  That is, use prettier's other parsers for languages inside those code fences.

  • <script> -> prettier's JavaScript formatter
  • <script type="application/x-typescript"> -> prettier's TypeScript formatter
  • <script type="anything/ends-with-json"> -> prettier's JSON formatter
  • <script type="text/markdown"> -> prettier's Markdown formatter
  • <style> -> prettier's CSS formatter

• Add support for other languages inside {% javascript %}, {% style %} and {% schema %} tagsc

  • {% javascript %} -> JS formatter
  • {% style %} -> CSS formatter
  • {% schema %} -> JSON formatter

• Add a new setting: embeddedSingleQuote

  • When true, single quotes will be preferred in embedded language blocks (JS, CSS, TS).
  • There's an upstream issue (shared by VueJS users) that prevents us from having two different "singleQuote" configurations in the same file.
  • Not having a setting for this caused a huge unecessary diff in Dawn. It looks like single in embedded and double for HTML is the way to go. THat'll be our default.

A note about Liquid-in-JS/CSS/JSON-in-Liquid

We'll try to use prettier's parser to pretty print your JS/CSS/JSON.

If your Liquid only appears in strings, you'll be able to use both. If you use Liquid as an expression, it won't work.

<script>
// won't work
const product = JSON.parse({{ product | json }})
</script>

<script>
// will work
const stuff = { property: "{{ setting.foo }}" }
</script>

When their parser throws, what we do is reindent the body of the tag and nothing more.

We do not attempt to format missing whitespace in Liquid-in-X-in-Liquid.

<script>
  const stuff = {
    property: "{{setting.foo|filter1|filter2:missing:whitespace:ugly}}"
  }
</script>

You'll still have to format that manually (sorry). We might come up with some genius idea to fix this in the future, but it won't be part of v1.0.0.

Examples

On dawn

https://github.com/Shopify/dawn/compare/wip%2Fprettier...Shopify:wip%2Fprettier-2

Fixes #7 Fixes #8