update docs about ssh support

apply suggestions from code review

Converted from getsops/sops@775335d
and getsops/sops@244a9a4

Co-authored-by: haoqixu <hq.xu0o0@gmail.com>
Co-authored-by: Felix Fontein <felix@fontein.de>
Signed-off-by: haoqixu <hq.xu0o0@gmail.com>
Signed-off-by: Felix Fontein <felix@fontein.de>

Author: felixfontein

content/en/docs/_index.md

@@ -256,7 +256,14 @@ 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 falls back 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`: