[v2.0.0-rc.0] Broken support for extended fence language

[simonbrunel]

This is a regression of the feature introduced by a5d0cce.

For example, using the same input as the unit test:

```js more words are ignored
var answer = 6 * 7;
```

```js
var answer = 6 * 7;
```

Running ESLint on the markdown above:

> eslint *.md


test.md
  6:1  error  Unexpected var, use let or const instead  no-var

✖ 1 problem (1 error, 0 warnings)

Should report 2 errors with the following config:

module.exports = {
  extends: 'plugin:markdown/recommended',
  rules: {
    'no-var': 'error'
  }
};

I haven't been able to run tests locally (failed to npm install this repo on Windows) but I think that the associated unit test doesn't guarantee that the returned block will be processed by ESLint. I guess the returned block.filename is '0.js more words are ignored' which doesn't pass the glob matching on this virtual block filename.

[btmills]

I guess the returned block.filename is '0.js more words are ignored' which doesn't pass the glob matching on this virtual block filename.

You were right! Thanks so much for the bug report. Fix is in #167.

[btmills]

I haven't been able to run tests locally (failed to npm install this repo on Windows)

Whoops. Thanks for reporting that as well. #168 should fix it.