🎉 init(cmake): init modern cmake template

tests/testlib.cpp

@@ -0,0 +1,11 @@
+#define CATCH_CONFIG_MAIN
+#include <catch2/catch.hpp>
+#include <modern/lib.hpp>
+
+TEST_CASE( "Quick check", "[main]" ) {
+    std::vector<double> values {1, 2., 3.};
+    auto [mean, moment] = accumulate_vector(values);
+
+    REQUIRE( mean == 2.0 );
+    REQUIRE( moment == Approx(4.666666) );
+}