initial description how to handle multiple board versions in Arduino IDE

extras/multiple_versions.md

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+# Using Multiple ESP32 Board Versions in Arduino IDE (Windows)
+
+Tested with: **Arduino IDE 2.3.5**\
+Target: Use multiple versions of **Espressif's ESP32 Arduino core** side-by-side in the Arduino IDE.
+
+---
+
+## ⚒️ Step-by-step Instructions
+
+### 1. 📂 Prepare Your Folder Structure
+
+Create a `hardware` folder inside your Arduino sketchbook:
+
+```text
+C:\Users\%USERNAME%\Documents\Arduino\hardware
+```
+
+Inside that, create a subfolder for your desired version:
+
+```text
+C:\Users\%USERNAME%\Documents\Arduino\hardware\espressif_2.0.17
+```
+
+Clone the ESP32 Arduino core into the `esp32` subfolder:
+
+```bash
+cd %USERPROFILE%\Documents\Arduino\hardware\espressif_2.0.17
+
+git clone https://github.com/espressif/arduino-esp32.git esp32
+
+cd esp32
+
+git checkout tags/2.0.17
+```
+
+This will download version 2.0.17 into the path:
+
+```text
+...\Arduino\hardware\espressif_2.0.17\esp32
+```
+
+### 2. 🔄 Restart Arduino IDE
+
+After restarting the Arduino IDE, you will now see both board versions:
+
+- The default one from Boards Manager
+- Your custom version from the Sketchbook
+
+Look for entries like:
+
+- `ESP32 Dev Module`
+- `ESP32 Dev Module (in Sketchbook) (espressif_2.0.17)`
+
+![grafik](https://github.com/user-attachments/assets/5fa68133-cdfc-461a-acec-9a76942a4a9d)
+
+
+---
+
+### 3. ⚠️ Compatibility with Arduino IDE < 2.x
+
+Older IDE versions may **not display version labels** in the board selection menu.
+
+To make your custom version distinguishable:
+
+1. Edit this file:
+
+   ```text
+   ...\Arduino\hardware\espressif_2.0.17\esp32\platform.txt
+   ```
+
+2. Add or modify the `name` field at the top:
+
+   ```ini
+   name=ESP32 Arduino (in Sketchbook) (espressif_2.0.17)
+   ```
+
+This ensures proper identification in older IDEs.
+
+---
+
+## ✅ Benefits
+
+- Use different versions of ESP32 platform for different projects
+- Test compatibility with older/newer SDKs
+- Avoid breaking changes from updates
+
+---
+
+## 💻 Optional: One-liner Script for Setup
+
+```bash
+cd %USERPROFILE%\Documents\Arduino\hardware
+
+mkdir espressif_2.0.17 && cd espressif_2.0.17
+
+git clone https://github.com/espressif/arduino-esp32.git esp32
+
+cd esp32 && git checkout tags/2.0.17
+```