support data URI's in image preview

[jogibear9988]

support data URI's for image preview

fixes https://github.com/microsoft/vscode/issues/237220

[jogibear9988]

It works, but the URI is used as the filename:

Is there a way to change this? I open via

				let img = vscode.Uri.parse('data:image/svg+xml;base64,' + itemResult.data);
				await vscode.commands.executeCommand('vscode.openWith', img, 'imagePreview.previewEditor');