VS Code Extension: Add a public API

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

Start by locating the VS Code extension's activation entry point and reviewing how vscode.extensions.getExtension("quarto.quarto").activate() currently behaves. Compare the requested integration with the linked vscode-gradle Extension.ts API example, then define the public API scope and verify that activation returns it.