Allow for conditional side-by-side or inline diffEditor

[NiloCK]

I like side-by-side diffs. I'm also pretty happy with inline diffs. What I don't like is finding myself looking at side-by-side diffs in a narrow editor window:

My suggestion aligns with responsive web design - the diffEditor should be configurable to run side-by-side above a certain breakpoint, and inline below.

proposed configuration flag:

diffEditor.renderInlineBreakpoint: number

The renderInlineBreakpoint value could be pixels (probably the easiest implementation path) or a character count (probably a finer-grained tool).

This flag would have no effect if diffEditor.renderSideBySide is set to false.

(Famous last words) This seems like a pretty straightforward patch to write. I could have a look at it myself if I receive some feedback to the effect that there are no anticipated blockers with respect to merging something like this into main.

[hediet]

This is actually a great idea!

I think we can enable this by default (900px seems like a good breakpoint width) to make the inline view feature more discoverable.
Also, we can add a menu entry "Use Inline View When Space Is Limited" that only shows when the inline view is shown because the space is limited:

Verification steps:

• Open the diff editor in side-by-side view
• Reduce the width
• Notice that the diff editor switches to inline view
• Notice that the ... menu has options to control this behavior

Expect the implementation in insiders end of next week.