Modified panel color

Author: darrenburns

src/textual/theme.py

@@ -72,6 +72,7 @@ def to_color_system(self) -> ColorSystem:
         error="#ba3c5b",
         success="#4EBF71",
         foreground="#e0e0e0",
+        panel="#2f3236",
         dark=True,
     ),
     "textual-light": Theme(