DEV-3389 docs(onlys):add subject

subjects/onlys/README.md

@@ -0,0 +1,16 @@
+## onlys
+
+### Instructions
+
+Write a program that displays an `S` character on the standard output. (and nothing else)
+
+### Usage
+
+```console
+$ go run .
+S
+$ go run . "a" "b"
+S
+$ go run . "a" "b" "c"
+S
+```