Support for p256tag and p256mlkem768tag recipients

Currently, when using an identity generated by [age-plugin-tpm](https://github.com/Foxboron/age-plugin-tpm) like `age1tag1...`, this is the output of sops encrypt: ``` Could not generate data key: [failed to encrypt new data key with master key "age1tag1...": failed to create writer for encrypting sops data key with age: failed to wrap key for recipient #0: tag plugin: couldn't start plugin: "tag" plugin not found: exec: "age-plugin-tag": executable file not found in $PATH] ``` Invoking age itself with the identity works fine. I think support for p256tag and p256mlkem768tag is generally missing. The old tpm tag works fine.