Add proper example for optional ref in root README

Author: neatudarius

README.md

@@ -69,28 +69,24 @@ The next code snippet shows optional reference support added in [`std::optional<
 #include <beman/optional/optional.hpp>
 ...
 
-{
-    // Empty optional example.
-    std::optional<int>             std_empty_opt;
-    beman::optional::optional<int> beman_empty_opt;
-    assert(!std_empty_opt.has_value() &&
-            !beman_empty_opt.has_value()); // or assert(!std_empty_opt && !beman_empty_opt);
-    std::cout << "std_vs_beman: .has_value() matches?: "
-              << (std_empty_opt.has_value() == beman_empty_opt.has_value() ? "yes" : "no") << "\n";
-}
+// Example from P2988R5: optional reference.
+
+struct Cat { ... };
+
+beman::optional::optional<Cat&> find_cat(std::string) { return {}; }
+beman::optional::optional<Cat&> do_it(Cat& cat) { return { cat }; }
 
-{
-    // Optional with value example.
-    std::optional<int>             std_opt   = 26;
-    beman::optional::optional<int> beman_opt = 26;
-    assert(std_opt.has_value() && beman_opt.has_value()); // or assert(std_opt && beman_opt);
-    assert(std_opt.value() == beman_opt.value());         // or assert(*std_opt == *beman_opt);
-    std::cout << "std_vs_beman: .value() matches?: " << (std_opt.value() == beman_opt.value() ? "yes" : "no")
-              << "\n";
+beman::optional::optional<Cat&> api() {
+    beman::optional::optional<Cat&> cat = find_cat("Fido");
+    return cat.and_then(do_it);
 }
+
+beman::optional::optional<Cat&> cat = api();
+
 ```
 
-Full code can be found in [./examples/optional_ref.cpp](./examples/optional_ref.cpp). Build and run instructions in [./examples/README.md](./examples/README.md).
+Full code can be found in [./examples/optional_ref.cpp](./examples/optional_ref.cpp). Build and run instructions in [./examples/README.md](./examples/README.md). Or try it on Compiler Explorer: [optional_ref.cpp@Compiler Explorer](https://godbolt.org/z/MxjdvTTov)
+
 
 ## How to Build