[Twig] Support CraftCMS css and js blocks

[oles]

I'm doing some silly stuff with CraftCMS, and seemingly my best option now is some template generated inline css.

CraftCMS provides some custom Twig functionality, and two of them are tags for css and js;

• https://craftcms.com/docs/3.x/dev/tags.html#css
• https://craftcms.com/docs/3.x/dev/tags.html#js

Example:

{% css %}
    .content {
        color: {{ entry.textColor }};
    }
{% endcss %}

I did not expect web-mode to handle these, but I did some searches to see if there was something I could do.

And I found a similar issue: https://github.com/fxbois/web-mode/issues/805#issuecomment-276258707

If this quite niche thing is within scope as well, I'll try to get a PR rolling!