[CMake] Add minimal cmake support

- CMake file only supports add_subdirectory workflow.
- Provides target Boost::conversion, but doesn't support
  installation or running unit tests.

CMakeLists.txt

@@ -0,0 +1,24 @@
+# Copyright 2019 Mike Dev
+# Distributed under the Boost Software License, Version 1.0.
+# See accompanying file LICENSE_1_0.txt or copy at https://www.boost.org/LICENSE_1_0.txt
+#
+# NOTE: CMake support for Boost.Conversion is currently experimental at best
+#       and the interface is likely to change in the future
+
+cmake_minimum_required( VERSION 3.5 )
+project( boost-conversion LANGUAGES CXX )
+
+add_library( boost_conversion INTERFACE )
+add_library( Boost::conversion ALIAS boost_conversion )
+
+target_include_directories( boost_conversion INTERFACE include )
+
+target_link_libraries( boost_conversion
+    INTERFACE
+        Boost::assert
+        Boost::config
+        Boost::smart_ptr
+        Boost::throw_exception
+        Boost::type_traits
+        Boost::typeof
+)