Use type-only imports

[not-matt]

❌ TS error on generated code when verbatimModuleSyntax is enabled

// Code generated by sqlc. DO NOT EDIT.

import mysql, { RowDataPacket, ResultSetHeader } from "mysql2/promise";
                ^^^^^^^^^^^^^  ^^^^^^^^^^^^^^^
                `'ResultSetHeader' is a type and must be imported using a 
                type-only import when 'verbatimModuleSyntax' is enabled.ts(1484)`

✅ Fixed by adding type keyword

import mysql, { type RowDataPacket, type ResultSetHeader } from "mysql2/promise";

Hopefully it is a simple addition to add the type keyword to these imports by default.
The imports are both interfaces so would only be used as types.
This change is also compatible if verbatimModuleSyntax is not enabled.