Currently we can query number as double or integer, but we can't reliable get value as 64-bit integer.
For big numbers the last digits are not precise for double and the numbers are too big for int32.
so we need:
inline fmx::int64 AsInt64 () const;
inline void AssignInt64 ( fmx::int64 that );
This would help plugin developers to receive/pass 64-bit numbers more precisely.