"999 is enough for anybody" triple-zero padding (#18)

When I hit 999 exercises, I will finally have reached the ultimate
state of soteriological release and no more exercises will be needed.
The cycle will be complete. All that will be left is perfect quietude,
freedom, and highest happiness.

exercises/015_for.zig

@@ -0,0 +1,27 @@
+//
+// Behold the 'for' loop! It lets you execute code for each
+// member of an array:
+//
+//     for (items) |item| {
+//
+//         // Do something with item
+//
+//     }
+//
+const std = @import("std");
+
+pub fn main() void {
+    const story = [_]u8{ 'h', 'h', 's', 'n', 'h' };
+
+    std.debug.print("A Dramatic Story: ", .{});
+
+    for (???) |???| {
+        if (scene == 'h') std.debug.print(":-)  ", .{});
+        if (scene == 's') std.debug.print(":-(  ", .{});
+        if (scene == 'n') std.debug.print(":-|  ", .{});
+    }
+
+    std.debug.print("The End.\n", .{});
+}
+// Note that "for" loops also work on things called "slices"
+// which we'll see later.