Moved plugins and refactor command system

- Moved plugins to apropriate sub folders
- Refactor command system with new add_command method and rename GetCommandSystemEvent to GetNewCommandSystemEvent
- Add RegisterCommandEvent for dynamic command registration
- Change footer container orientation to VERTICAL
- Add search-highlight tag to source buffer
- Add file change detection (deleted, externally modified) in source_file
- Add JSON prettify option to source view popup menu
- Enable hexpand on VTE widget
- Update plugins_controller_mixin to use widget_registry

src/libs/dto/code/register_command_event.py

@@ -0,0 +1,20 @@
+# Python imports
+from dataclasses import dataclass, field
+
+# Lib imports
+import gi
+gi.require_version('GtkSource', '4')
+
+from gi.repository import GtkSource
+
+# Application imports
+from ..base_event import BaseEvent
+
+
+
+@dataclass
+class RegisterCommandEvent(BaseEvent):
+    command_name: str = ""
+    command: callable = None
+    binding_mode: str = ""
+    binding: str      = ""