docs(displayP): created new subject

- subject for this exercise was missing

docs(displayP): fix name

- fixed folder name / exercise name

docs(displayP): removed wrong folder

docs(displayP): fix subject grammar

- fixed grammar

docs(displayp): ran prettier format

subjects/displayp/README.md

@@ -0,0 +1,19 @@
+## displayp
+
+### Instructions
+
+Write a program that displays a character `P` followed by a newline `\n`.
+
+### Usage
+
+```console
+$ go run . | cat -e
+P$
+$
+$ go run . "a" "b" | cat -e
+P$
+$
+$ go run . "a" "b" "c" | cat -e
+P$
+$
+```