feat: Added arena_alloc

Added arena_alloc and decided to change the arena pointer type from void *
to uint8_t * because i need to support 1 byte pointer arithmetic, thought of
using uintptr_t but not sure, the support seems really weird from what i read
online so i'm sticking with good old uint8_t * (wich i know works).

include/arena.h

@@ -7,7 +7,7 @@
 #include <stdbool.h>
 
 typedef struct {
-    void *data;
+    uint8_t *data;
     size_t size;
     size_t offset;
 } Arena;
@@ -24,7 +24,7 @@ typedef struct {
     bool is_valid;
     union {
         ArenaErr err;
-        void *pointer;
+        uint8_t *pointer;
     };
 } ArenaPointer;