Split vulkan_base into smaller units

Closes #30. This is a basic refactoring of the graphics module, so
everything won't be in single file.

utilities/file_utils.hpp

@@ -0,0 +1,15 @@
+#ifndef RSE_FILE_UTILS_HPP
+#define RSE_FILE_UTILS_HPP
+
+#include <vector>
+#include <string>
+
+namespace rse::utils::file
+{
+
+std::vector<char> read_file(const std::string& fileName);
+
+}
+
+#endif
+