Attempt to fix the GCC build

CMakeLists.txt

@@ -36,8 +36,7 @@ target_compile_features(continuable-base
     cxx_defaulted_functions
     cxx_nullptr
     cxx_trailing_return_types
-    cxx_return_type_deduction
-    $<$<COMPILE_FEATURES:cxx_std_17>:cxx_std_17>)
+    cxx_return_type_deduction)
 
 add_library(continuable INTERFACE)
 

include/continuable/continuable-base.hpp

@@ -250,8 +250,7 @@ public:
   /// http_request("github.com")
   ///   .then([](std::string github) { })
   ///   .catching([](std::error_condition error) {
-  ///     // Handle the error here
-  ///     // ...
+  ///     error.message(); // Handle the error here
   ///   });
   /// ```
   ///

include/continuable/continuable.hpp

@@ -34,6 +34,7 @@
 #include "function2/function2.hpp"
 
 #include <continuable/continuable-base.hpp>
+#include <continuable/continuable-promise-base.hpp>
 
 namespace cti {
 // clang-format off

test/playground/test-playground.cpp

@@ -22,4 +22,6 @@
 
 #include <continuable/continuable.hpp>
 
-int main(int, char**) { return 0; }
+int main(int, char**) {
+  return 0;
+}