update checkbox docstring (#850)

added more description to color-scheme docs

pynecone/components/forms/checkbox.py

@@ -13,6 +13,9 @@ class Checkbox(ChakraComponent):
     tag = "Checkbox"
 
     # Color scheme for checkbox.
+    # Options:
+    # "whiteAlpha" | "blackAlpha" | "gray" | "red" | "orange" | "yellow" | "green" | "teal" | "blue" | "cyan"
+    # | "purple" | "pink" | "linkedin" | "facebook" | "messenger" | "whatsapp" | "twitter" | "telegram"
     color_scheme: Var[str]
 
     # "sm" | "md" | "lg"