Nunjucks v2.2.4

Fixes:

• fixed the error "no such target scope:source.css.js-template#rule-list-body"
  that prevented the syntax from loading

Refactor:

• removed the njk-js, njk-css, njk-json and njk-css-rule-list contexts

Known limitations:

• template tags inside <script>, <style>, JSON scripts and style
  attributes are not highlighted