add warning for unrecognised output format

[danielt998]

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https://github.com/danielt998/HanziToAnki/blob/5794c022dcf058b950a47d87a864fd57ada76ee3/src/main/java/hanziToAnki/ArgParser.java#L66

we should issue a warning in the default case for an unrecognised format and state that we are falling back to Anki. And add Anki as a separate switch case