extensions/markdown-language-features/src/workspaceContents.ts/VsCodeMdWorkspaceContents/getMarkdownDocument
class VsCodeMdWorkspaceContents:	public async getMarkdownDocument(resource: vscode.Uri): Promise<SkinnyTextDocument | undefined> {
		const matchingDocument = vscode.workspace.textDocuments.find((doc) => doc.uri.toString() === resource.toString());
		if (matchingDocument) {
			return matchingDocument;
		}

		try {
			const bytes = await vscode.workspace.fs.readFile(resource);

			// We assume that markdown is in UTF-8
			const text = this.utf8Decoder.decode(bytes);
			return new InMemoryDocument(resource, text, 0);
		} catch {
			return undefined;
		}
	}