frp: add uci config integration

Signed-off-by: Richard Yu <yurichard3839@gmail.com>

net/frp/files/frpc.config

@@ -0,0 +1,23 @@
+config init
+	option stdout 1
+	option stderr 1
+	option user frpc
+	option group frpc
+	option respawn 1
+#	OS environments pass to frp for config file template, see
+#	https://github.com/fatedier/frp#configuration-file-template
+#	list env 'ENV_NAME=value'
+#	Config files include in temporary config file.
+#	list conf_inc '/etc/frp/frps.d/frpc_full.ini'
+
+config conf 'common'
+	option server_addr 127.0.0.1
+	option server_port 7000
+#	List options with name="_" will be directly appended to config file
+#	list _ '# Key-A=Value-A'
+
+config conf 'ssh'
+	option type tcp
+	option local_ip 127.0.0.1
+	option local_port 22
+	option remote_port 6000