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

plugins/code/completers/lsp_completer/provider_response_cache.py

@@ -0,0 +1,55 @@
+# Python imports
+from concurrent.futures import ThreadPoolExecutor
+
+# Lib imports
+import gi
+gi.require_version('GtkSource', '4')
+
+from gi.repository import GtkSource
+
+# Application imports
+from libs.event_factory import Code_Event_Types
+
+from core.widgets.code.completion_providers.provider_response_cache_base import ProviderResponseCacheBase
+
+
+
+class ProviderResponseCache(ProviderResponseCacheBase):
+    def __init__(self):
+        super(ProviderResponseCache, self).__init__()
+
+        self.executor = ThreadPoolExecutor(max_workers = 1)
+        self.matchers: dict = {}
+
+
+    def process_file_load(self, event: Code_Event_Types.AddedNewFileEvent):
+        buffer = event.file.buffer
+        self.executor.submit(self._handle_change, buffer)
+
+    def process_file_close(self, event: Code_Event_Types.RemovedFileEvent):
+        ...
+
+    def process_file_save(self, event: Code_Event_Types.SavedFileEvent):
+        ...
+
+    def process_file_change(self, event: Code_Event_Types.TextChangedEvent):
+        buffer = event.file.buffer
+        self.executor.submit(self._handle_change, buffer)
+
+    def _handle_change(self, buffer):
+        ...
+
+
+    def filter(self, word: str) -> list[dict]:
+        return []
+
+    def filter_with_context(self, context: GtkSource.CompletionContext)  -> list[dict]:
+        proposals = [
+            {
+                "label": "LSP Class",
+                "text": "LSP Code",
+                "info": "A test LSP completion item..."
+            }
+        ]
+
+        return proposals