Add support for multi-value `SCOREINIT`/`SCOREDIFF` metadata (e.g. `650,1000`)

[vivaria]

In the short-term, this should be an incredibly simple change, since TDMX only cares about the last value (shinuti). (value.split(",")[-1])

In the long term, we may want to add a way for users to specify which of the values they want encoded into their fumens.