typescript definitions expose constructors even when none exist

[OmarTawfik]

When a WIT resource doesn't define a constructor, jco generates a JS constructor by default, that just throws when called:

jco/crates/js-component-bindgen/src/transpile_bindgen.rs

Lines 621 to 623 in fe90d2f

	constructor () {{
	throw new Error('\"{local_name}\" resource does not define a constructor');
	}}

But the TypeScript definitions ignore that fact, and don't generate anything, which means that tsc will still consider it to contain a built-in constructor that can be called, so static analysis will fail to catch this error, producing bugs that only surface at runtime.

Instead, I suggest generating a private constructor(); in TypeScript definitions, so that can be prevented at build time.

[guybedford]

This is a great suggestion, thank you.