Typora app should not change file extension to `.markdown` when Saving As

[neuromachina]

Description Typora app should not change the extension to .markdown when .md is set as default in the Prefs/Settings and invoking the command "Save As"

To Reproduce Within the Typora app I invoked the Save As command on exsiting Typora file in the side bar when this manifested.

Expected behavior

1. Expected same extension of the file I was "SAVING As..."
2. Expect the default extension set in the Preferences (if #1 expectation is not applied)

In this situation the Default File Type/Ext is set to: .md

Typora Version 1.12.3