doc: add photo caption handler to readme

README.md

@@ -173,6 +173,7 @@ b, err := bot.New("YOUR_BOT_TOKEN_FROM_BOTFATHER", opts...)
 - `WithMiddlewares(middlewares ...Middleware)` - add middlewares
 - `WithMessageTextHandler(pattern string, matchType MatchType, handler HandlerFunc)` - add handler for Message.Text field
 - `WithCallbackQueryDataHandler(pattern string, matchType MatchType, handler HandlerFunc)` - add handler for CallbackQuery.Data field
+- `WithPhotoCaptionHandler` - add handler for Message.Caption field
 - `WithDefaultHandler(handler HandlerFunc)` - add default handler
 - `WithDebug()` - enable debug mode
 - `WithErrorsHandler(handler ErrorsHandler)` - add errors handler
@@ -189,7 +190,7 @@ b, err := bot.New("YOUR_BOT_TOKEN_FROM_BOTFATHER", opts...)
 
 ## Message.Text and CallbackQuery.Data handlers
 
-For your convenience, you can use `Message.Text` and `CallbackQuery.Data` handlers.
+For your convenience, you can use `Message.Text`, `CallbackQuery.Data` and `Message.Caption` handlers.
 
 An example: