Added Jetbrains Rider external exec flags example

getting_started/editor/external_editor.rst

@@ -35,3 +35,5 @@ Some example Exec Flags for various editors include:
 +---------------------+-----------------------------------------------------+
 | atom/sublime text   | {file}:{line}                                       |
 +---------------------+-----------------------------------------------------+
+| jetbrains rider     | --line {line} {file}                                |
++---------------------+-----------------------------------------------------+