initialize spec macro and standards

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

kaptan-spec/Cargo.toml

@@ -0,0 +1,13 @@
+[package]
+name = "kaptan-spec"
+version.workspace = true
+edition.workspace = true
+license.workspace = true
+repository.workspace = true
+rust-version.workspace = true
+
+[lib]
+proc-macro = true
+
+[dev-dependencies]
+trybuild = "1.0"