add datastream support, refactor custom completion (#32)

cmd/root.go

@@ -90,6 +90,7 @@ func Main() int {
 			Cluster(conf),
 			Ccr(conf),
 			Index(conf),
+			Datastream(conf),
 			Shard(conf),
 			Snapshot(conf),
 			Node(conf),
@@ -146,6 +147,20 @@ friends.#(first%"D*").last         >> "Murphy"
 friends.#(first!%"D*").last        >> "Craig"
 friends.#(nets.#(=="fb"))#.first   >> ["Dale","Roger"]
 
+To extract more than one field, use:
+
+{"ns":source.namespace_name,"time":source.@timestamp} >>
+
+{
+  "ns": "3f80316965c64405-275a75782e984bcc8d82",
+  "time": "2026-06-10T04:23:38.914080361+00:00"
+}
+{
+  "ns": "3f80316965c64405-f0e1dcef668e45bb9afd",
+  "time": "2026-06-10T09:39:00.554892542+00:00"
+}
+
+
 Documentation: https://github.com/tidwall/gjson/blob/master/SYNTAX.md`
 
 	return &cli.Command{