Add deserialiseOnly

[AshleyYakeley]

It seems for many applications, you don't need to store the schema at all, is that correct?

In that case, it seems this would be a useful function:

deserialiseOnly :: forall a. Serialise a => ByteString -> Either WineryException a
deserialiseOnly bs = do
    decoder <- getDecoder $ schema $ Nothing @a
    return $ evalDecoder decoder bs

[fumieval]

The intended usecase is to store the schema first and encode any number of values independently using serialiseOnly, so users should still read the stored schema. However, if people are using winery as an alternative for binary, I don't object to adding deserialiseOnly either

[AshleyYakeley]

I'm currently investigating the behaviour of the various serialisation libraries, and Winery is nice because of its compact representation, provided it can be used without schema storage.

[fumieval]

I see, no objections then