Revise docs.

doc/src/language/for.md

@@ -14,7 +14,9 @@ let s = "hello, world!";
 
 for ch in s {
     if ch > 'z' { continue; }   // skip to the next iteration
+
     print(ch);
+
     if x == '@' { break; }      // break out of for loop
 }
 
@@ -23,21 +25,27 @@ let array = [1, 3, 5, 7, 9, 42];
 
 for x in array {
     if x > 10 { continue; }     // skip to the next iteration
+
     print(x);
+
     if x == 42 { break; }       // break out of for loop
 }
 
 // The 'range' function allows iterating from first to last-1
 for x in range(0, 50) {
     if x > 10 { continue; }     // skip to the next iteration
+
     print(x);
+
     if x == 42 { break; }       // break out of for loop
 }
 
 // The 'range' function also takes a step
 for x in range(0, 50, 3) {      // step by 3
     if x > 10 { continue; }     // skip to the next iteration
+
     print(x);
+
     if x == 42 { break; }       // break out of for loop
 }
 
@@ -47,7 +55,9 @@ let map = #{a:1, b:3, c:5, d:7, e:9};
 // Property names are returned in unsorted, random order
 for x in keys(map) {
     if x > 10 { continue; }     // skip to the next iteration
+
     print(x);
+
     if x == 42 { break; }       // break out of for loop
 }