base64 - encode/decode base64 (UTF-8 safe)

Usage:
  curl --data-binary @- https://ttykit.com/base64/encode   < input
  curl --data-binary @- https://ttykit.com/base64/decode   < input

Query params:
  urlsafe=1   use the base64url alphabet (-_, no padding) instead of standard base64

Examples:
  echo -n "hello world" | curl --data-binary @- https://ttykit.com/base64/encode
  echo -n "aGVsbG8gd29ybGQ=" | curl --data-binary @- https://ttykit.com/base64/decode