OP#188 add Readme partl

README.md

@@ -40,6 +40,12 @@ Configurable options:
 - MemorySwapMax via `ps_swap_mem`
 - OOMScoreAdjust via `ps_oom_score`
 - GOMAXPROCS via `ps_max_procs`
+- external remote write ( writing to a remote instance like pg-adapter):
+  - `ps_write_external` true enables it
+  - `ps_external_url` must be a valid full url
+  - `ps_auth_ext_user`must be a valid user
+  - `ps_auth_ext_pass`must be a valid password
+
 
 ## Repo Documentation