Moved exercises to exercises because exercises

exercises/01_hello.zig

@@ -0,0 +1,22 @@
+//
+// Oh no! This program is supposed to print "Hello world!" but it needs
+// your help!
+//
+// 
+// Zig functions are private by default but the main() function should
+// be public.
+//
+// A function is declared public with the "pub" statement like so:
+//
+//     pub fn foo() void {
+//         ...
+//     }
+//
+// Try to fix the program and run `ziglings` to see if it works!
+//
+const std = @import("std");
+
+fn main() void {
+    std.debug.print("Hello world!\n", .{});
+}
+