Prompt to install Quarto extension when working with Qmd or Rmd files

[jmcphers]

Via @wch

It would be great if the user didn’t have to go out and find an extension for Positron to recognize Rmd files. Or at least Positron should direct the user to download the appropriate extension if they open the file.

I am pretty sure we could do this cheaply because there is already infrastructure to prompt users to install an extension to handle the file type they just opened.

positron/src/vs/workbench/contrib/extensions/browser/fileBasedRecommendations.ts

Lines 134 to 141 in 4e94ea8

	/**
	* Prompt the user to either install the recommended extension for the file type in the current editor model
	* or prompt to search the marketplace if it has extensions that can support the file type
	*/
	private promptImportantRecommendations(uri: URI, model: ITextModel, extensionRecommendations?: IStringDictionary<IFileOpenCondition[]>): void {
	if (model.isDisposed()) {
	return;
	}

[juliasilge]

We are pretty sure that no one (?) sees this in Positron and we aren't sure why at the moment; this may be worth a time boxed investigation sooner rather than later.

[juliasilge]

This came up in usability testing with @t-kalinowski.

[juliasilge]

We bundle the Quarto extension now so this is no longer a problem.