add ES256 functionality example

Author: bourgeoa

examples/ES256.js

@@ -0,0 +1,62 @@
+const crypto = require('isomorphic-webcrypto')
+const JWA = require('../src/jose/JWA')
+
+let privateKey, publicKey
+
+console.log('Testing ES256 support in @solid/jose library...')
+
+crypto.subtle
+
+  // use webcrypto to generate an ECDSA keypair
+  .generateKey(
+    {
+      name: 'ECDSA',
+      namedCurve: 'P-256',
+      hash: {
+        name: 'SHA-256'
+      }
+    },
+    true,
+    ['sign', 'verify']
+  )
+
+  // use key with JWA to create a signature
+  .then(keypair => {
+    privateKey = keypair.privateKey
+    publicKey = keypair.publicKey
+    
+    console.log('✅ ES256 key pair generated successfully')
+    
+    return JWA.sign('ES256', privateKey, 'header.payload')
+  })
+
+  // verify the signature
+  .then(signature => {
+    console.log('✅ ES256 signature created:', signature.substring(0, 20) + '...')
+    
+    return Promise.all([
+      Promise.resolve(signature),
+      JWA.verify('ES256', publicKey, signature, 'header.payload'),
+      JWA.verify('ES256', publicKey, signature, 'wrong'),
+    ])
+  })
+
+  // look at the output
+  .then(result => {
+    console.log('✅ ES256 verify results:')
+    console.log('  Signature:', result[0].substring(0, 20) + '...')
+    console.log('  Valid signature verified:', result[1])
+    console.log('  Invalid signature verified:', result[2])
+    
+    if (result[1] === true && result[2] === false) {
+      console.log('🎉 ES256 is FULLY FUNCTIONAL in @solid/jose!')
+    }
+  })
+
+  // look at any errors
+  .catch(error => {
+    console.error('❌ ES256 test failed:', error.message)
+    if (error.message.includes('normalizedAlgorithm.importKey')) {
+      console.error('❌ This is the importKey error we were seeing!')
+    }
+  })