Add unit tests

Yay tests!

test/System/Buffer.test.cpp

@@ -0,0 +1,11 @@
+#include <SFML/System/Buffer.h>
+
+#include <catch2/catch_test_macros.hpp>
+
+TEST_CASE("[System] sfBuffer")
+{
+    sfBuffer* buffer = sfBuffer_create();
+    CHECK(sfBuffer_getSize(buffer) == 0);
+    CHECK(sfBuffer_getData(buffer) == 0);
+    sfBuffer_destroy(buffer);
+}