Suggestion: find a better way to indicate a partial code snippet

[rynowak]

Describe the bug

When we have a code snippet that's partial (showing changes to only part of a large file) we usually terminate the code snippet with ... or just omit the other parts of the file.

The suggestion is that we could find a way to show the rest of the code (collapsed by default) or to fade or pixelate the text of the sample that aren't the focus.

AB#9831