fix(hit-res): use template literals to assert type of stringified nums

[tharropoulos]

Change Summary

Since text_match_info returns best_field_score and score as numbers in string format, Typescript's template literals allow to assert that the underlying type is a number. This change provides enhancements to the overall typesafety of the client.

PR Checklist

• I have read and signed the Contributor License Agreement.