Add examples/sort-music.sh: music file sorter using find loop
Add examples/sort-music.sh: music file sorter using find loop

share/doc/modernish/examples/sort-music.sh:
- Added. This demonstrates:
  . the safe mode with -k
  . command hardening, including optionally running with
    PATH=/dev/null for extra bug-proofness
  . var/cmd/procsubst: portable process substitution
  . the 'find' loop
  . the new assign command from var/assign
  . var/string: replacein, trim, tolower
  . 'is', 'str' and 'let' as replacements for test/[

modernish/modernish