age: add page (#5758)

pages/common/age.md

@@ -0,0 +1,28 @@
+# age
+
+> A simple, modern and secure file encryption tool.
+> More information: <https://age-encryption.org>.
+
+- Generate an encrypted file that can be decrypted with a passphrase:
+
+`age --passphrase --output {{path/to/encrypted_file}} {{path/to/unencrypted_file}}`
+
+- Generate a key pair, saving the private key to an unencrypted file and printing the public key to stdout:
+
+`age-keygen --output {{path/to/file}}`
+
+- Encrypt a file with one or more public keys that are entered as literals:
+
+`age --recipient {{public_key_1}} --recipient {{public_key_2}} {{path/to/unencrypted_file}} --output {{path/to/encrypted_file}}`
+
+- Encrypt a file with one or more public keys that are specified in a recipients file:
+
+`age --recipients-file {{path/to/recipients_file}} {{path/to/unencrypted_file}} --output {{path/to/encrypted_file}}`
+
+- Decrypt a file with a passphrase:
+
+`age --decrypt --output {{path/to/decrypted_file}} {{path/to/encrypted_file}}`
+
+- Decrypt a file with a private key file:
+
+`age --decrypt --identity {{path/to/private_key_file}} --output {{path/to/decrypted_file}} {{path/to/encrypted_file}}`