Toggle option to hide "Recent files" section

[dayeggpi]

Added a simple toggle option in Settings > Appearance to hide/show the recent files section on app startup

[dayeggpi]

second part of PR is :

• Improvement: When in rendered markdown view with file that was never saved/created, control+s doesnt work (nothing happens). also added save/save as in menu.
• Improvement: allow user to switch to rendered view without saving/creating file : if file was created and user switches to rendered view, it would save file automatically or ask user to save file before (depending on "save automatically" option), no way to see rendered view until file is saved.
• Bug fix: "autosave ON + confirm before save ON" now triggers prompt to ask user if they want to save (every 1.5seconds)

Let me know if you prefer for me to separate them