update doc

Author: dongyuwei

config/frp/frp.md

@@ -1,4 +1,5 @@
 ## frp_0.60.0
 - server: frp_0.60.0_linux_amd64, `./frps -c frps.toml`
 - client: frp_0.60.0_darwin_amd64, `./frpc -c frpc.toml`
-- domain in config/config.exs shoule be updated to the **same** domain in customDomains frpc.toml, set both to `tmpmail.work`.
+- domain in config/config.exs shoule be updated to the **same** domain in customDomains frpc.toml, set both to `tmpmail.work`.
+- visist http://tmpmail.work:8080/ to verify the tmp mail serice.