docs(wave): add subject of function wave (js piscine checkpoint)

subjects/wave/README.md

@@ -0,0 +1,34 @@
+## wave
+
+### Instructions
+
+Create a function that turns a string into a Mexican Wave. 
+You will be passed a string and you must return that string in an array where an uppercase letter is a person standing up. 
+
+### Expected function
+
+```js
+function wave(str) {
+}
+```
+### Usage
+
+Here is a possible program to test your function
+
+```js
+    wave("holla")
+    console.log("\n")
+    wave("welcome to 01")
+    console.log("\n")
+    wave("welcome13")
+
+```
+And its output :
+
+```console
+$ node .
+["Holla", "hOlla", "hoLla", "holLa", "hollA"]
+wrong string format
+["Welcome13","wElcome13","weLcome13","welCome13","welcOme13","welcoMe13","welcomE13"]
+```
+