Incompatible version of Bash on macOS

[snowskeleton]

The interactiveAAXtoMP3 script uses the -i option, which is not supported on the default version of bash that ships with macOS (GNU bash, version 3.2.57(1)-release). Updating with homebrew (brew install bash) installs a working version (GNU bash, version 5.1.16(1)-release). Might be able to add a check somewhere to see which version of bash is being used and adapt accordingly.