Improvements for RTL languages

This PR addressed a few issues for RTL languages I encountered when reviewing #3680. This PR solves:

- An issue that a horizontal scrollbar was shown for an RTL language. This was because `margin-left` had to be `margin-right` for RTL languages on line 452.

- Some icons in the viewer were not mirrored properly, which needs to be the case for RTL languages. I've mirrored all icons that actually look different when mirrored to solve this issue.