Allow authors to use render syntax with curly braces `{{ content }}`

[crphang]

Currently authors have no way to render {{ content }} easily due to Vue. The only workaround is adding appropriate span tags

<span>{</span>{ content <span>}</span>}.

Rendering such syntax could be required for certain authors attempting to teach various Domain Specific Language that could contain such syntax, one example is Latex.

With work on #1049 and #1047, MarkBind currently allows special tags that retains curly braces instead of being removed from Nunjucks over repeated rendering if {% raw %} {% endraw%} is being used. However, due to Vue, we are still unable to render {{ }} as it is being used for interpolation. See: vuejs/vue#4223.

A possible experience to overcome that would be to introduce a new plugin:

<escape>
{%raw%}
{{ any content }} 
{%endraw%}
</escape>

Would be even better if <escape> automatically adds required nunjucks escaping.

References and potential solution:

#1049 (comment)

For general use, we could create a special component, something like that acts the same as a in addition to appending {% raw %} {% endraw %}

[crphang]

To add on to the proposed possible solution, it might not be necessary to use special tag in this, but doing so can have a consistent solution to solve #1196 which is due to markdown-it-attr.