Add sample of logical operators in if statements

Fixes #494

examples/if-else/if-else.go

@@ -19,6 +19,12 @@ func main() {
 		fmt.Println("8 is divisible by 4")
 	}
 
+	// Logical operators like `&&` and `||` are often
+	// useful in conditions.
+	if 7%2 == 0 || 8%2 == 0 {
+		fmt.Println("either 8 or 7 are even")
+	}
+
 	// A statement can precede conditionals; any variables
 	// declared in this statement are available in the current
 	// and all subsequent branches.

examples/if-else/if-else.hash

@@ -1,2 +1,2 @@
-d6a962236fc1296684cd1ffb2d95d131ed84abde
-U7xcpdutgCJ
+152124e287cd55e549bc29bcb8693bf260d1b3ab
+hTOHdmUcUxz

examples/if-else/if-else.sh

@@ -1,6 +1,7 @@
 $ go run if-else.go 
 7 is odd
 8 is divisible by 4
+either 7 or 8 are even
 9 has 1 digit
 
 # There is no [ternary if](https://en.wikipedia.org/wiki/%3F:)