[guide] [react] add missing PascalCase guidance for prop names

react/README.md

@@ -267,7 +267,7 @@ This style guide is mostly based on the standards that are currently prevalent i
 
 ## Props
 
-  - Always use camelCase for prop names.
+  - Always use camelCase for prop names, or PascalCase if the prop value is a React component.
 
     ```jsx
     // bad
@@ -280,6 +280,7 @@ This style guide is mostly based on the standards that are currently prevalent i
     <Foo
       userName="hello"
       phoneNumber={12345678}
+      Component={SomeComponent}
     />
     ```