dev: add module example

editors/vscode/samples/cmake-workspace/greeting_module.cppm

@@ -0,0 +1,14 @@
+module;
+
+#include <string>
+#include <string_view>
+
+export module sample.greeting;
+
+export namespace sample {
+
+std::string build_module_greeting(std::string_view name) {
+    return "Hello, " + std::string(name) + " from the C++20 module sample.";
+}
+
+}