Avoid useless whitespace control

[yguedidi]

Would you accept in core a rule that forbid using whitespace control if the previous/next character is not a whitespace?

So forbid for example:

<div>{{- var -}}</div>

I think it's doable in a similar way to TrailingSpace by going through tokens.
I first thought about the RegEngineRule but it seems that it's focused on what happen inside Twig markup

---

As an extension of the idea, would be great to forbid it in block overrides too, like:

{% extends '...' %}

{%- block foo -%}
    ...
{%- endblock -%}

But here I have no idea how this is doable