chore: pubspec - Add topic crypto

See: https://dart.dev/tools/pub/pubspec#topics

Other packages with this topic include:
https://pub.dev/packages?q=topic%3Acrypto

Author: jonasfj

cryptography/pubspec.yaml

@@ -4,6 +4,8 @@ homepage: https://github.com/dint-dev/cryptography
 description:
   Cryptographic algorithms for encryption, digital signatures, key agreement, authentication, and
   hashing. AES, Chacha20, ED25519, X25519, Argon2, and more. Good cross-platform support.
+topics:
+  - crypto
 
 environment:
   sdk: '>=3.1.0 <4.0.0'

cryptography_flutter/pubspec.yaml

@@ -1,9 +1,11 @@
 name: cryptography_flutter
+version: 2.3.2
+homepage: https://github.com/dint-dev/cryptography
 description:
   Makes 'package:cryptography' use platform APIs in Android, iOS, and Mac OS X. The package can
   make performance up to 100 times better.
-version: 2.3.2
-homepage: https://github.com/dint-dev/cryptography
+topics:
+  - crypto
 
 environment:
   sdk: '>=3.1.0 <4.0.0'