Added few methods to JS Array (#1865)

js-array.md

@@ -14,6 +14,8 @@ list = [a,b,c,d,e]
 ```bash
 list[1]                 // → b
 list.indexOf(b)         // → 1
+list.lastIndexOf(b)     // → 1
+list.includes(b)        // → true
 ```
 
 ### Subsets
@@ -81,6 +83,10 @@ list.splice(2, 1)       // → [c]  list == [a,b,d,e]
 .filter(n => ...) => array
 ```
 
+```bash
+.forEach(n => ...)
+```
+
 ```bash
 .find(n => ...)  // es6
 .findIndex(...)  // es6