Strategy for converting a block of source code into pretty-printed HTML. SourceCodeFormatters MUST be forgiving:
they will be dealing with user-supplied input, so they can't afford to blow up on bad data.
Inform the CodeMacro which languages this formatter supports. So if someone writes {code:java}, then only
the formatter that returns "java" from this method will be used to format it.
Returns:
an array of languages that this formatter supports