extensions/markdown-language-features/src/preview/preview.ts/MarkdownPreview/getLocalResourceRoots
class MarkdownPreview:	private getLocalResourceRoots(): ReadonlyArray<vscode.Uri> {
		const baseRoots = Array.from(this._contributionProvider.contributions.previewResourceRoots);

		const folder = vscode.workspace.getWorkspaceFolder(this._resource);
		if (folder) {
			const workspaceRoots = vscode.workspace.workspaceFolders?.map(folder => folder.uri);
			if (workspaceRoots) {
				baseRoots.push(...workspaceRoots);
			}
		} else {
			baseRoots.push(uri.Utils.dirname(this._resource));
		}

		return baseRoots;
	}