Add -ssh: an opt-in built-in SSH server (public keys only, sessions only)

.env.example

@@ -14,6 +14,11 @@ BAMBOO_TOKEN=
 #BAMBOO_DISCOVER_PORTS=22,80,443,8000-8010
 #BAMBOO_DISCOVER_RATE=50
 
+# Run a built-in SSH server (public keys only). The keys that may sign in go in authorized_keys in the data folder.
+#BAMBOO_SSH=1
+#BAMBOO_SSH_LISTEN=127.0.0.1:2222
+#BAMBOO_SSH_KEYS=
+
 # Folder for this agent's WireGuard key.
 #BAMBOO_DATA=./bamboo-data