VSCE: Automate rendering of user's color theme

Created by: jjinnii

The expected behavior of the VSCE is to pull in a user's color theme palette for all UI elements, including text color, background color for containers, icon colors, etc. This allows the extension to feel more "native' and integrated to VS Code extension and prevents scenarios in which there is a harsh contrast btw a user's default color palette and switching to our extension.

It's important that we check with multiple color palettes and ensure that we are pulling in these color themes in an effective and accessible way -- this will define at a glance how the extension looks to a user.