docs: fix simple typo, purpsosely -> purposely

There is a small typo in miniz.h.

Should read `purposely` rather than `purpsosely`.

miniz.h

@@ -220,7 +220,7 @@ enum
 #define MZ_DEFLATED 8
 
 /* Heap allocation callbacks.
-Note that mz_alloc_func parameter types purpsosely differ from zlib's: items/size is size_t, not unsigned long. */
+Note that mz_alloc_func parameter types purposely differ from zlib's: items/size is size_t, not unsigned long. */
 typedef void *(*mz_alloc_func)(void *opaque, size_t items, size_t size);
 typedef void (*mz_free_func)(void *opaque, void *address);
 typedef void *(*mz_realloc_func)(void *opaque, void *address, size_t items, size_t size);