ESM support & various other compat improvements

[toptobes]

woohoo yay 100th pr yay whatever ok with that out of the way, this PR:

Allows astra-db-ts to target both CJS & ESM ❗

astra-db-ts has been updated to dual-target both CommonJS (CJS) and ECMAScript Modules (ESM).

While the package itself has been converted into pure ESM, it now transpiles in a way that should seamlessly support both module systems.

Users who were previously using astra-db-ts as CJS may continue to do so without any issues.

Types were verified using @arethetypeswrong/cli and some manual testing.

Import path conversions were done using ts2esm.

The new dist structure looks like so:

dist
|- esm/
|--- *transpiled js files*
|--- package.json containing `{"type":"module"}`
|--- index.d.ts containing `export type * from '../astra-db-ts.d.ts'`
|- cjs/
|--- *transpiled js files*
|--- package.json containing `{"type":"commonjs"}`
|--- index.d.ts containing `export type * from '../astra-db-ts.d.ts'`
|- astra-db-ts.d.ts

And the root package.json was updated to hold the new values:

"type": "module",
"main": "dist/cjs/index.js",
"exports": {
  ".": {
    "require": {
      "types": "./dist/cjs/index.d.ts",
      "default": "./dist/cjs/index.js"
    },
    "import": {
      "types": "./dist/esm/index.d.ts",
      "default": "./dist/esm/index.js"
    }
  },
  "./package.json": "./package.json"
},

ESlint configs were updated to be type-aware

consistent-type-* lints were necessary to update to ESM (requiring types to be explicitly imported/exported with import type/export type)

As a result, this surfaced a wave of new linting errors, which have been fixed—though none of these changes should introduce any functional differences.

Removes hard dependencies on fetch-h2 and events for better environment compatibility

It's simply too painful & error-prone to deal with optional deps between CJS, ESM, and different runtime environments in general

• require() vs await import()
• cloudflare events compat only works w/ node:events
• top-level await not always supported
• and we don't even speak of AMD or UMD

To simplify everything:

fetch-h2 is no longer the default HTTP client for astra-db-ts.

astra-db-ts now defaults to using the standard fetch API.

If you want to use fetch-h2, you need to install it yourself (npm i fetch-h2) and pass it as an option:

import { DataAPIClient } from '@datastax/astra-db-ts'
import * as fetchH2 from 'fetch-h2'

const client = new DataAPIClient({
   httpOptions: { client: 'fetch-h2', fetchH2 },
});

DataAPIClient is no longer a Node-compliant EventEmitter

It now uses a custom, micro EventEmitter implementation (how original, I know 🙄)

This improves compatibility across different environments while keeping things simple.

// More methods may very well come in the future
declare class MicroEmitters<Events extends Record<string, (...args: any[]) => void>> {
  on  <E extends keyof Events>(event: E, listener: Events[E]): () => void;
  off <E extends keyof Events>(event: E, listener: Events[E]): void;
  once<E extends keyof Events>(event: E, listener: Events[E]): () => void;
  emit<E extends keyof Events>(event: E, ...args: Parameters<Events[E]>): boolean;
}

As a bonus, the typed-emitter dependency was able to be removed, since MicroEmitter is natively typed

Uses tslib w/ importHelpers to save a few bytes of bundle size

yaaaaayyyyyyyy