Support type-only imports when using verbatimModuleSyntax

[superflav]

TypeScript 5.0 Release introduced verbatimModuleSyntax option which simplifies import elision rules when handling type only imports. With the new option, the user must explicitly specify which imports are type only.

Assuming Type is only used as a type, this:

import { MyContext } from "./myContext";

should be updated to this:

import type { MyContext } from "./myContext";

Currently, however, openapi-codegen has no support for this yet causing issues for projects using verbatimModuleSyntax.

For reference, GraphQL allows this to be toggled on & off via their useTypeImports codegen config option.