What is the Web Cryptography API equivalent of crypto.sign() and crypto.createPrivateKey()?

[guest271314]

I'm trying to create a Signed Web Bundle to be used in an Isolated Web App in the browser based on code in a Node.js-based package https://github.com/guest271314/webbundle.

How to substitute Web Cryptography API for node:crypto usage here https://www.npmjs.com/package/wbn-sign?activeTab=code at node-crypto-signing-strategy

import crypto from 'crypto';
import { checkIsValidEd25519Key } from '../utils/utils.js';
// Class to be used when signing with parsed `crypto.KeyObject` private key
// provided directly in the constructor.
export class NodeCryptoSigningStrategy {
    privateKey;
    constructor(privateKey) {
        this.privateKey = privateKey;
        checkIsValidEd25519Key('private', privateKey);
    }
    async sign(data) {
        return crypto.sign(/*algorithm=*/ undefined, data, this.privateKey);
    }
    async getPublicKey() {
        return crypto.createPublicKey(this.privateKey);
    }
}

with Web Cryptography API equivalent here

// Option 3: With ones own CustomSigningStrategy class implementing
// ISigningStrategy.
const { signedWebBundle } = await new wbnSign.IntegrityBlockSigner(
  webBundle,
  new (class {
    async sign(data: Uint8Array): Promise<Uint8Array> {
      // E.g. connect to one's external signing service that signs the payload.
    }
    async getPublicKey(): Promise<KeyObject> {
      /** E.g. connect to one's external signing service that returns the public
       * key.*/
    }
  })()
).sign();