Support official .yaml extension for YAML files

[vcschapp]

Description

This trivial change enables support for the .yaml file extension, which is the official file extension for YAML per the YAML FAQ.

Testing

No new tests added, but existing ones pass:

$ npm test
...
Test Suites: 9 passed, 9 total
Tests:       44 passed, 44 total
Snapshots:   0 total
Time:        1.604 s, estimated 2 s
Ran all test suites.

[tomcollins]

Hi @vcschapp. Thanks for raising this PR. The change looks fine.

We probably want to update this line for completeness:

json-schema-static-docs/lib/renderer-markdown.js

Line 19 in caed396

(value.match(/^(.+)#/) || value.match(/^(.+)\.(json|yml)$/))

But happy to approve as things stand.

[tomcollins]

I make the renderer change in #101

[vcschapp]

Thanks @tomcollins !