Highlight the changeset editor when the comment is empty

[ogadaki]

Change the style of the changeset editor when the comment is empty to explicitly indicate the user what he has to do.

This PR is a minimal change to fix #4613. It only modifies the CSS for the changeset editor.

I've just seen there is another PR for this issue (#4621) which implements some other features that might be helpfull. I still submit mine in case a simpler fix is preferable (also, it's my first one for iD and I chose a "good first issue").

(closes #4613)

[bhousel]

This is perfect, thanks @nnodot 👍

[althio]

Thanks @nnodot for the PR and @bhousel for merging this in.
I like the results with a simple CSS fix.

One question though:
What is the expected behaviour when the changeset comment field is pre-filled by an external application?

[ogadaki]

@althio I was asking myself the same question. I guess one might want to have the same behavior as the empty comment one's (as in this PR)?

[bhousel]

I did not test the behavior with a pre-filled comment, but I'm assuming it would work the same way (that's good!). If the changeset comment field has some value, the field will be classed as present during the update selection.

iD/modules/ui/field.js

Lines 142 to 144 in baeff8f

	container
	.classed('modified', isModified())
	.classed('present', isPresent())