extensions/markdown-language-features/src/workspace.ts/VsCodeMdWorkspace/getAllMarkdownDocuments
class VsCodeMdWorkspace:	async getAllMarkdownDocuments(): Promise<ITextDocument[]> {
		const maxConcurrent = 20;

		const foundFiles = new ResourceMap<void>();
		const limiter = new Limiter<ITextDocument | undefined>(maxConcurrent);

		// Add files on disk
		const resources = await vscode.workspace.findFiles('**/*.md', '**/node_modules/**');
		const onDiskResults = await Promise.all(resources.map(resource => {
			return limiter.queue(async () => {
				const doc = await this.getOrLoadMarkdownDocument(resource);
				if (doc) {
					foundFiles.set(resource);
				}
				return doc;
			});
		}));

		// Add opened files (such as untitled files)
		const openTextDocumentResults = await Promise.all(vscode.workspace.textDocuments
			.filter(doc => !foundFiles.has(doc.uri) && this.isRelevantMarkdownDocument(doc)));

		return coalesce([...onDiskResults, ...openTextDocumentResults]);
	}