VS Code Extension: Add a public API

[pogi7]

Initial Reasoning for Feature

In the VSCode Extension, I was trying to interface with it using the VSCode API. Specifically I was trying to run

vscode.extensions.getExtension("quarto.quarto").activate().then((quartoApi) => {
// Do something with api 
});

but I get undefined from the quartoApi variable.

Feature Request

Please add a public API to the VSCode Extension.

It would be very helpful to be able to integrate with the quarto.quarto VSCode extension through an API similar to how Microsoft has APIs for their VSCode extensions such as the vscjava.vscode-gradle VSCode extension