Update tiny_stack_allocator.c

I am trying to use this as a library for esphome I think this will fix an error I'm getting

```
src/tiny_stack_allocator.c:16:5: error: unknown type name 'max_align_t'
     max_align_t data[max(_size, sizeof(max_align_t)) / sizeof(max_align_t)];```

Author: RebbePod

src/tiny_stack_allocator.c

@@ -4,6 +4,7 @@
  */
 
 #include <stddef.h>
+#include <stdalign.h>
 #include <stdint.h>
 #include "tiny_stack_allocator.h"
 #include "tiny_utils.h"