Setup submodule funny business

.gitmodules

@@ -0,0 +1,3 @@
+[submodule "web5-spec"]
+	path = web5-spec
+	url = https://github.com/TBD54566975/web5-spec

Makefile

@@ -1,3 +1,11 @@
+bootstrap:
+# Initialize submodules
+	git submodule update --init
+# Initialize sparse checkout in the `web5-spec` submodule
+	git -C web5-spec config core.sparseCheckout true
+# Sparse checkout only the `test-vectors` directory from `web5-spec`
+	git -C web5-spec sparse-checkout set test-vectors
+# Update submodules so they sparse checkout takes effect
+	git submodule update
 format:
 	swift format --in-place --recursive .
-