Add live Markdown editing, colours and files in the tree

Backend/Settings.py

@@ -45,6 +45,9 @@ DefaultSettings: dict[str, Any] = {
     "ConfirmBeforeDelete": True,
     "VisibleInBlame": True,
     "ShowBlameAvatars": False,
+    # "Live": Markdown is edited where it's shown rendered (Obsidian-style
+    # live preview). "Separate": rendered View and raw Edit are two modes.
+    "MarkdownEditing": "Live",
 }
 
 DefaultThemesDirectory = ApplicationDirectory / "DefaultThemes"