add alternate location of this directory (espressif#732)

Author: tedder

docs/arduino-ide/debian_ubuntu.md

@@ -19,3 +19,17 @@ Installation instructions for Debian / Ubuntu OS
   python get.py
   ```
 - Restart Arduino IDE
+
+
+
+- If you have Arduino.app installed to /Applications/, modify the installation as follows, beginning at `mkdir -p ~/Arduino...`:
+
+```bash
+  cd /Applications/Arduino_*/Contents/java/hardware/
+  mkdir -p espressif && \
+  cd espressif && \
+  git clone https://github.com/espressif/arduino-esp32.git esp32 && \
+  cd esp32 && \
+  git submodule update --init --recursive && \
+  cd tools && \
+  python get.py```