Feature: Set preview range on the current media

Description of change

There are two ways to set the preview range:

• Box Select P (default Blender): Set the Preview range doing a box selection in the sequencer.
• Current Shift + P: Set the Preview Range around the current media (white highlighted one)

Created a menu at the bottom of the UI. In Advanced Drawing mode, only the box select is available.

Closes #255 (closed)

How to test it

• Click on Set Preview Range

Checklist

Please check if your MR fulfills the following requirements:

• Unit tests have been added, if needed
• Documentation have been updated, if needed
• Build was run locally and any changes were pushed
• Lint has passed locally without error
• Package.py have been updated, if needed
• CHANGELOG.md have been updated, if needed
• Version numer has been tagged, if needed

FYI: @awesome_dev_too