Add age plugin support

See https://github.com/str4d/rage/tree/main/age-plugin.

Example usage:

	RAGE_DIR=$PWD/../Rust/rage
	(cd $RAGE_DIR; cargo build --all)
	export PATH=$PATH:$RAGE_DIR/target/debug

	age-plugin-trezor -i "John Doe" | tee trezor.id
	R=$(grep recipient trezor.id | cut -f 3 -d ' ')

	date | tee msg.txt
	rage -er $R < msg.txt > enc.txt
	rage -di trezor.id < enc.txt

libagent/formats.py

@@ -101,7 +101,7 @@ def parse_pubkey(blob):
 
 def _decompress_ed25519(pubkey):
     """Load public key from the serialized blob (stripping the prefix byte)."""
-    if pubkey[:1] == b'\x00':
+    if pubkey[:1] in {b'\x00', b'\x01'}:
         # set by Trezor fsm_msgSignIdentity() and fsm_msgGetPublicKey()
         return nacl.signing.VerifyKey(pubkey[1:], encoder=nacl.encoding.RawEncoder)
     else: