Add support for `PG::Numeric` type

[fridgerator]

Add support for `PG::Numeric` type

[jwoertink]

Decimal is already supported, right? According to this documentation

The types decimal and numeric are equivalent. Both types are part of the SQL standard.

decimal | variable | user-specified precision, exact | up to 131072 digits before the decimal point; up to 16383 digits after the decimal point
-- | -- | -- | --
numeric | variable | user-specified precision, exact | up to 131072 digits before the decimal point; up to 16383 digits after the decimal point

So maybe this just becomes an alias?

[fridgerator]

yeah an alias might work 👍