export the tokenize function directly
export the parse function directly
account for multiple transpiler support
add support for base case formatters

Since we format certain strings using bracket-notation (e.g. # => ${#}),
we want to apply these transformations at the very end when we are done
parsing the message. Base case formatters hook into this moment and
allow us to format strings as they leave the parser.
`#` chars in plural format messages should be output as `${#}`