initialize spec macro and standards

Signed-off-by: Onur Özkan <work@onurozkan.dev>

kaptan-spec/tests/ui/fail_missing_sidecar.rs

@@ -0,0 +1,8 @@
+use kaptan_spec::spec;
+
+#[spec("fail_missing_sidecar.v0.1.0.spec.md")]
+struct MissingSpec;
+
+fn main() {
+    let _ = core::mem::size_of::<MissingSpec>();
+}