keys: Add new readline command to cut the whole line.

Author: Niloth-p

zulipterminal/config/keys.py

@@ -383,6 +383,11 @@ class KeyBinding(TypedDict):
         'help_text': 'Cut backwards to the start of the current word',
         'key_category': 'editor_text_manipulation',
     },
+    'CUT_WHOLE_LINE' + READLINE_SUFFIX: {
+        'keys': ['meta x'],
+        'help_text': 'Cut the current line',
+        'key_category': 'text_operations',
+    },
     'PASTE_LAST_CUT' + READLINE_SUFFIX: {
         'keys': ['ctrl y'],
         'help_text': 'Paste last cut section',