gRPC client for Dwarf

Use with dwarf microservice on a node web server.
Use DWARF_GRPC_SERVER env var to set the gRPC server.

``typescript
import { shorten } from "dwarf-client";

async function main() {
try {
const shortenedUrls = await shorten(["http://google.com", "http://whatever.com"]);
console.log(shortenedUrls); // -> { urls: ["short-link-1", "short-link-2"] }
} catch (err) {
console.error(err);
}
}
``