added instructions for finding Meta key on MacOS

added link to macos-meta.md

Author: 8alpreet

microbit/src/06-serial-communication/macos-meta.md

@@ -0,0 +1,10 @@
+# Minicom on macOS
+
+### Finding Your Command Key
+
+```shell
+$ # start minicom in setup mode
+$ minicom -s
+```
+1. Select `Keyboard and Misc Functions`
+2. Look at the first option `A - Command key is` 

microbit/src/06-serial-communication/nix-tooling.md

@@ -91,3 +91,5 @@ Mac, the shortcuts start with the `Meta` key. Some useful commands below:
 - `Ctrl+A` + `Q`. Quit with no reset
 
 > **NOTE** Mac users: In the above commands, replace `Ctrl+A` with `Meta`.
+
+[Can't find the Meta key?](macos-meta.md)