[Feature request] Add option to change default new file to markdown

[Dadangdut33]

Hello and thank you so much for the beautiful app. I've been using it a lot and would like to request a feature if possible.

Is your feature request related to a problem? Please describe. I would like to have the new file that is created in the app to be .md instead of .txt. I know that we can just rename it but it would great if there is a default setting that you can set.

Describe the solution you'd like Add option to allow change the default new file type

Additional context Notepads version 1.5.3.0