Update index.md (#264)

* Update index.md

Add thonny as a possible python editor for Micro:Bit

* Update index.md

Co-authored-by: Mark <[email protected]>

Author: bdelaup

software/index.md

@@ -99,6 +99,8 @@ Here's a non-exhaustive list of possible code editors for use with the micro:bit
 
 - [PyCharm (with MicroPython plugin, can also flash to micro:bit)](https://plugins.jetbrains.com/plugin/9777-micropython)
 
+- [Thonny (You will need to change the interpreter in Tools > Options > Interpreter)](https://thonny.org/)
+
 
 ## From coding environment to micro:bit