Add syntax highlighting for pipeline config

[lafriks]

Screenshots:

[anbraten]

@lafriks Can we use prismjs to highlight yaml errors? I think it would be quite nice to show errors of the configuration using our editor/view in the long term.

[lafriks]

@anbraten where are yaml errors displayed? you mean my other PR?

[anbraten]

@lafriks Yep. The idea to show the config file and underline / highlight the incorrect part as you can see by the screenshot in #276. We could also use that to have some kind of an editor in the long term to allow users to paste and check their config without committing it.

[lafriks]

I can add that later on when this is merged

[lafriks]

Only drawback would be that it would require parsing yaml parser error messages

[anbraten]

I can add that later on when this is merged

It's definitely a task for a new PR. I just wanted to make sure prismjs supports additional highlighting like this underline wave other editors use to show errors in general. Couldn't find this exact use-case from a short search, but it seems primsjs supports some kind of plugin mechanism that could be used for it.