🎉 init(cmake): init modern cmake template

tests/CMakeLists.txt

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+# Testing library
+FetchContent_Declare(
+  catch
+  GIT_REPOSITORY https://github.com/catchorg/Catch2.git
+  GIT_TAG v2.13.6)
+FetchContent_MakeAvailable(catch)
+# Adds Catch2::Catch2
+
+# Tests need to be added as executables first
+add_executable(testlib testlib.cpp)
+
+# I'm using C++17 in the test
+target_compile_features(testlib PRIVATE cxx_std_17)
+
+# Should be linked to the main library, as well as the Catch2 testing library
+target_link_libraries(testlib PRIVATE modern_library Catch2::Catch2)
+
+# If you register a test, then ctest and make test will run it.
+# You can also run examples and check the output, as well.
+add_test(NAME testlibtest COMMAND testlib) # Command can be a target

tests/testlib.cpp

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+#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) );
+}