Updated documentation for "import std;"

Author: rollbear

ChangeLog

@@ -1,3 +1,12 @@
+        * Support for "import std;" is enabled by defining the macro
+          STRONG_TYPE_IMPORT_STD_LIBRARY. This has currently only been
+          tested on MSVC with C++20 and C++23. Other compilers may or
+          may not work at this point. You can also run the unit-tests
+          with "import std;" by adding the CMake option
+          -DSTRONG_TYPE_IMPORT_STD_LIBRARY=yes
+
+          Huge thangs to David Hunter for contributing this addition.
+
         * Make strong::range work with range types that only has
           const_iterator types (e.g. std::set). Thanks David Feltell for
           reporting the problem.

README.md

@@ -68,6 +68,9 @@ A strong type can be used as an NTTP ([Non Type Template
 Parameter](https://en.cppreference.com/w/cpp/language/template_parameters)), if
 the underlying type can be, for compilers and standards that support it.
 
+*strong_type* uses the std library module, with `import std;` if you
+define the macro `STRONG_TYPE_IMPORT_STD_LIBRARY=1`.
+
 # <A name="modifiers"/> Modifiers:
 
 * <A name="affine_point"/>`strong::affine_point<D>` allows instances to be
@@ -681,10 +684,14 @@ cmake <strong_type_dir> -DSTRONG_TYPE_UNIT_TEST=yes
 cmake --build .
 ```
 
-This will produce the test programs `self_test`, and conditionally also
+You can also add the option `-DSTRONG_TYPE_IMPORT_STD_LIBRARY=yes` if your
+development environment supports C++20 "`import std;`" 
+
+The build will produce the test programs `self_test`, and conditionally also
 `test_fmt8`,`test_fmt9`, `test_fmt10` and `test_fmt11`, depending on which version(s) of
 [`{fmt}`](https://fmt.dev/latest/index.html)
 
+
 N.B. Microsoft Visual Studio MSVC compiler < 19.22 does not handle `constexpr`
 correctly. Those found to cause trouble are disabled for those versions.