update docs about ssh support

Signed-off-by: haoqixu <hq.xu0o0@gmail.com>

Author: haoqixu

README.rst

@@ -233,7 +233,13 @@ The contents of this key file should be a list of age X25519 identities, one
 per line. Lines beginning with ``#`` are considered comments and ignored. Each
 identity will be tried in sequence until one is able to decrypt the data.
 
-Encrypting with SSH keys via age is not yet supported by SOPS.
+Encrypting with SSH keys via age is also supported by SOPS. You can use SSH public keys
+("ssh-ed25519 AAAA...", "ssh-rsa AAAA...") as age recipients when encrypting a file.
+When decrypting a file, SOPS will look for `~/.ssh/id_ed25519` and fallbacks to
+`~/.ssh/id_rsa`. You can specify the location of the private key manually by setting
+the environment variableuse **SOPS_AGE_SSH_PRIVATE_KEY_FILE**.
+
+Note that only `ssh-rsa` and `ssh-ed25519` are supported.
 
 A list of age recipients can be added to the ``.sops.yaml``: