examples: prepare for adding more examples

build.zig

@@ -23,7 +23,7 @@ pub fn build(b: *std.build.Builder) void {
     const test_step = b.step("test", "Run library tests");
     test_step.dependOn(&main_tests.step);
 
-    const example = b.addExecutable("hello-triangle", "examples/main.zig");
+    const example = b.addExecutable("hello-triangle", "examples/triangle/main.zig");
     example.setTarget(target);
     example.setBuildMode(mode);
     example.addPackage(pkg);