kconfig: added experimental feature list

Kconfig

@@ -507,3 +507,10 @@ mainmenu "Espressif IoT Development Framework Configuration"
 
             Note you should still enable a certain experimental feature option to use it, and you
             should read the corresponding risk warning and known issue list carefully.
+
+            Current experimental feature list:
+
+            - CONFIG_ESPTOOLPY_FLASHFREQ_120M
+            - CONFIG_SPIRAM_SPEED_120M
+            - CONFIG_SPI_FLASH_32BIT_ADDR_ENABLE
+            - CONFIG_FREERTOS_USE_KERNEL_10_5_1