Implement String structure and update Location/Token to use it

v0/string.h

@@ -0,0 +1,20 @@
+/**
+ * Contains the definition of the String structure, which is a simple representation of a string in C.
+ */
+#ifndef STRING_H
+#define STRING_H
+
+#include <stddef.h>
+
+/**
+ * A simple string structure that holds a pointer to the character data and its length.
+ */
+typedef struct {
+    /// @brief A pointer to the character data of the string.
+    char* data;
+
+    /// @brief The length of the string.
+    size_t length;
+} String;
+
+#endif