beautify 1st part of the tutorial

1-js/4-data-structures/10-arguments-pseudoarray/2-sum-arguments/solution.md

@@ -5,7 +5,7 @@
 function sum() {
   var result = 0;
 
-  for(var i=0; i<arguments.length; i++) {
+  for (var i = 0; i < arguments.length; i++) {
     result += arguments[i];
   }
 

1-js/4-data-structures/10-arguments-pseudoarray/2-sum-arguments/task.md

@@ -8,7 +8,7 @@
 sum() = 0
 sum(1) = 1
 sum(1, 2) = 3
-sum(1, 2 ,3) = 6
+sum(1, 2, 3) = 6
 sum(1, 2, 3, 4) = 10
 ```