Highlight incorrect indentation in red

[microbit-robert]

Highlight incorrect indentation in some shade of red with some amount of opacity in an attempt to make indentation errors more recognisable and easier to fix.

E.g.:

We won't know the users intentions, so we need to decide whether we highlight all preceding space in red, or just the minimum amount of preceding space that makes the indentation invalid.

[jaustin]

I think it should be the latter - IE "just the minimum amount of preceding space that makes the indentation invalid."

[microbit-matt-hillsdon]

One to discuss as I'm not sure whether or not we still have consensus here.