Addition of an ESBuild sample

[jasonwilliams]

As there is more migration to ESBuild (even internally in VS Code itself) from Webpack we should have an ESBuild sample extension.
This is much faster than the webpack setup, plus there are less dependencies and less configuration. On top of that, with Webpack being deprecated in favour of Turbopack it doesn't make sense to keep promoting it as the default build config for extensions.

This extension also supports building for web extensions by building both a Desktop and Web version of the extension in parallel. This provides a destination to point new users to when they want to build hybrid extensions in a modern way,

The VSCode docs already reference building with ESBuild so it felt right there was a sample extension to accompany it.