Implement growing arena

mem/include/arena/mem_arena.h

@@ -4,4 +4,12 @@
 #include "aliases.h"
 #include <stdbool.h>
 
+typedef struct growing_arena Arena;
+
+bool mem_arena_init(Arena **arena, u64 base_capacity);
+void *mem_arena_alloc(Arena *arena, u64 size);
+void *mem_arena_alloc_aligned(Arena *arena, u64 size, u64 alignment);
+void mem_arena_clear(Arena *arena);
+void mem_arena_free(Arena **arena);
+
 #endif // !MEM_ARENA_H