Use isolatedModules for easier compatibility with Deno (and others)

[bradenmacdonald]

This PR changes the driver's TypeScript code to use TypeScript's stricter isolatedModules flag.

isolatedModules is required to support some transpilers that operate on a single file at a time, so they can tell which imports/exports contain only type information and are safe to discard. This change is more "strict" and does not change the API, so is completely backwards compatible.

Rationale: The reason for this PR is to allow a common codebase to work for both Node.js and Deno. While TypeScript/Node don't care if isolatedModules is enabled or not, Deno requires it. So this is a prerequisite to supporting Deno. See the relevant forum discussion. I will soon be opening a PR that shows how to generate a Deno driver, which depends on this change.

Without this change, Deno will report this TypeScript error when trying to transpile the driver code:

Re-exporting a type when the '--isolatedModules' flag is provided requires using 'export type'.

[bigmontz]

🥇

Thanks for your contribution.

Just waiting the pipeline go green to