Updated Flashing (markdown)

Flashing.md

@@ -107,10 +107,16 @@ Tutorials for setting up development environments if you want to modify the code
 - [**PlatformIO**](PlatformIO) -  setup and configure [PlatformIO](https://platformio.org) for Tasmota compilation and upload
 - [**PlatformIO CLI**](PlatformIO-CLI) - how to flash Tasmota using the PlatformIO command line interface on Linux
 - [**PlatformIO-Core**](Create-your-own-Firmware-Build-without-IDE) - automate firmware builds using PlatformIO-Core and flash with esptool
-- [**Arduino IDE**](Arduino-IDE) - setup and configure Arduino IDE for Tasmota compilation and upload
 - [**Visual Studio Code**](Visual-Studio-Code) -  setup and configure [Visual Studio Code](https://code.visualstudio.com) with PlatformIO for Tasmota
+- [**Arduino IDE**](Arduino-IDE) - setup and configure Arduino IDE for Tasmota compilation and upload
+
+If you use PlatformIO, to be sure that you have the latest build of the ESP Core, first delete the following folders in your current `.platformio` folder:
+- Everything in `.platformio/platforms`  
+- All folders that begin with `framework...` in `.platformio/packages`  
+
+## Online Compilers
+_**Can only create a firmware binary.** Use one of the [tools](Prerequisites#flashing-tool) to flash it to your device._
 - [**Gitpod**](Compiling-Tasmota-on-Gitpod) - compile your own binary in the cloud using [Gitpod](https://www.gitpod.io/).  
- _**Can only create a firmware binary.** Use one of the [tools](Prerequisites#flashing-tool) to flash it to your device._
 - [**TasmoCompiler**](https://github.com/benzino77/tasmocompiler) - simple web GUI to compile Tasmota with your own settings
 
 # OTA Flashing Tools