Update suggestion component with custom render

The following discussion from gitlab-ce!25211 should be addressed:

@pslaughter started a discussion: (+1 comment)

thought: I wonder if it'd be better to transform this noteHTML with a custom render function, rather than mounting it, and then manually mounting Vue components ontop of it. 🤔... I can foresee us wanting to do this with things other than suggestions so maybe a general decorated_markdown component which houses this special render function... Definitely out of scope for this MR, but I'd like to know what you think @ntepluhina 😄