Document that parseUnits now throws on empty input (since 2.55.4)

[alvinlicro]

Since 2.55.4, parseUnits (and parseEther / parseGwei) throws on inputs it used to accept:

import { parseUnits } from 'viem'

parseUnits('', 18)
// 2.55.2: 0n
// 2.55.4+: throws Value.InvalidDecimalNumberError

The same applies to '.', '-' and '-.'.

This came from #4859 / #4860, but those PRs' changeset was removed, so the release notes don't mention it. Apps that pass raw form input to parseUnits (an empty amount field, for example) crash after upgrading.

Could the parseUnits docs state that empty or partial inputs throw InvalidDecimalNumberError, and could the changelog note it as a behavior change?