Custom CSS remaining set on new documents and sessions

[paulojraposo]

Lovely editor, thanks!

I would like to have the app remember and stay set on a custom CSS between sessions and .md files, so that the user doesn't have to always select it again each time (as I seem to have to do on version 1.95 on Ubuntu). Related to issue 124 (#124), but I notice that the app does actually remember my custom CSS in the input window, it just doesn't use that on new documents, instead going back to the default styling. This is all that keeps me from using it as my daily driver.

Thanks!