Add CI for CMake project + consumer test

test/exampleProject/CMakeLists.txt

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+# Project testing to consume Boost.Nowide
+cmake_minimum_required(VERSION 3.8.0)
+project(nowide_example_project)
+
+find_package(boost_nowide 10.0 REQUIRED)
+
+add_executable(example example_main.cpp)
+target_link_libraries(example PRIVATE Boost::nowide)
+enable_testing()
+add_test(NAME example COMMAND example)

test/exampleProject/example_main.cpp

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+//
+//  Copyright (c) 2019 Alexander Grund
+//
+//  Distributed under the Boost Software License, Version 1.0. (See
+//  accompanying file LICENSE_1_0.txt or copy at
+//  http://www.boost.org/LICENSE_1_0.txt)
+//
+
+#include <boost/nowide/args.hpp>
+#include <boost/nowide/convert.hpp>
+
+int main(int argc, char **argv, char **env)
+{
+    boost::nowide::args _(argc, argv, env);
+    if(argc < 1)
+        return 1;
+    if(boost::nowide::narrow(boost::nowide::widen(argv[0])) != argv[0])
+        return 1;
+    return 0;
+}