Updated cursor positioning description for File open()
Updated cursor positioning description for File open()

Added more details about the cursor offsets for the different ModeFlags
in the `File` class.

(cherry picked from commit 5e77eea2167db1f3c3d974ebfda54dc67b9e9519)

ex/godot,ex/godot,ex/godot,ex/godot,ex/godot,ex/godot,ex/godot,ex/godot