GSoC 2021 - Week 8 - Tempo Popup Improvements & Fixes

Hi everyone! I spent the last week working on various improvements and bug fixes to the tempo popup. The most important of which are:
1. Positioning: The tempo popup appears to the side of the element, if it is too close to the bottom edge of the screen
2. Tab View Styling: The active tab is now highlighted.
3. Bug Fix: Prevent users from deleting part of the tempo equation through keyboard input
4. Bug Fix: Visibility toggle now works as expected with newly added tempo elements

You can find a full list of changes over the past week in my PR here