Produce browser bundle with tsdown

[nroponmain]

This change adds output that bundles external dependencies so the output can run directly in the browser.
Tsdown doesn't allow turning off code splitting so there is an output file for src/index.ts and src/patterns/index.ts.

Iife produces dist/browser/index.iife.js and dist/browser/patterns/index.iife.js.

Usage example:

<script src="./dist/browser/index.iife.js"></script>
<script src="./dist/browser/patterns/index.iife.js"></script>
<script>
     (async () => {
         const client = new Buttplug.ButtplugClient("ws://127.0.0.1:12345", {
              logger: Buttplug.consoleLogger,
         });
         const engine = new ButtplugPatterns.PatternEngine(client);
         await client.connect();
     )();
</script>

Esm bundle gets placed into dist/browser/index.mjs and dist/browser/feature-*.mjs.

Usage example:

<script type="module">
    import { ButtplugClient, consoleLogger } from "./dist/browser/index.mjs";
    import { PatternEngine } from "./dist/browser/patterns/index.mjs";

    const client = new ButtplugClient("ws://127.0.0.1:12345", {
        logger: consoleLogger,
    });
    const engine = new ButtplugPatterns.PatternEngine(client);
    await client.connect();
</script>