Precise locations for number errors

Currently if [NumberParser](https://github.com/kson-org/kson/blob/e08abcc33e546070a3f3262bf86a5aecec987141/src/commonMain/kotlin/org/kson/parser/NumberParser.kt) detects a bad character in a number, we anchor the error to the whole number. The work in https://github.com/kson-org/kson/pull/286 should allow us to report the precise location of the bad char.