For a full featured command line interface, see https://github.com/yadayadajaychan/zwc
'message' refers to the utf‐8 text which will be visible to viewers.
'data' is the data to be encoded into zero‐width utf‐8 characters and inserted
into the 'message'.
'text' is the final product with the encoded data hidden in the 'message'.
To encode, enter into the first box the 'data',
then the string 'EOF' on its own line,
then the message, and press 'encode'.
For example,
This is a secret message!
EOF
Hello!
To decode, enter the 'text' into the second box and press 'decode'.
Press 'clear' to clear both boxes.