feat(snippets): add a `Dynamic Left Sidebar`

[Ender-Wang]

Dynamic Left Sidebar Description

• Makes the left sidebar dynamic, so it only shows when you hover over it and pushes the main content to the right.

Motivation

• Previously, I made a New Hover Panel #778 that fixed the legacy Hover Panels. But after some time using it, I found it blocks the beginning of a playlist(can be anything) when I hover the left sidebar that activates the hovering, which is the expected hovering behavior, but it's kinda annoying. Then I made this one to be like when you hover the left side edge, the LeftSidebar appears and pushes the content to the right so nothing is blocked.