Extract comments into README for ssh-agent plugin

plugins/ssh-agent/README.md

@@ -0,0 +1,38 @@
+# ssh-agent plugin
+
+This plugin starts automatically `ssh-agent` to set up and load whichever
+credentials you want for ssh connections.
+
+To enable it, add `ssh-agent` to your plugins:
+
+```zsh
+plugins=(... ssh-agent)
+```
+
+## Instructions
+
+To enable **agent forwarding support** add the following to your zshrc file:
+
+```zsh
+zstyle :omz:plugins:ssh-agent agent-forwarding on
+```
+
+To **load multiple identities** use the `identities` style, For example:
+
+```zsh
+zstyle :omz:plugins:ssh-agent identities id_rsa id_rsa2 id_github
+```
+
+To **set the maximum lifetime of the identities**, use the `lifetime` style.
+The lifetime may be specified in seconds or as described in sshd_config(5)
+(see _TIME FORMATS_). If left unspecified, the default lifetime is forever.
+
+```zsh
+zstyle :omz:plugins:ssh-agent lifetime 4h
+```
+
+## Credits
+
+Based on code from Joseph M. Reagle: http://www.cygwin.com/ml/cygwin/2001-06/msg00537.html
+
+Agent-forwarding support based on ideas from Florent Thoumie and Jonas Pfenniger