feat: project skeleton, core types and math with transform tests

tests/CMakeLists.txt

@@ -0,0 +1,8 @@
+add_executable(plot_tests
+  main.cpp
+  test_transform.cpp
+)
+target_link_libraries(plot_tests PRIVATE plot::core)
+plot_apply_warnings(plot_tests)
+
+add_test(NAME plot_tests COMMAND plot_tests)