Reintroduce C++ support and add usage tests for C++ (#4)

Reviewed-on: #4
Co-authored-by: Abdelrahman <said.abdelrahman89@gmail.com>
Co-committed-by: Abdelrahman <said.abdelrahman89@gmail.com>

tests/allocator/test_allocator.cc

@@ -0,0 +1,18 @@
+#include "test_allocator.h"
+#include "wapp.h"
+#include <stdbool.h>
+#include <stdlib.h>
+
+TestFuncResult test_arena_allocator(void) {
+  Allocator allocator = wapp_mem_arena_allocator_init(4096);
+  bool result         = allocator.obj != nullptr && allocator.alloc != nullptr &&
+                        allocator.alloc_aligned != nullptr &&
+                        allocator.realloc != nullptr && allocator.realloc_aligned != nullptr &&
+                        allocator.free == nullptr;
+  void *ptr           = wapp_mem_allocator_alloc(&allocator, 20);
+  result              = result && (ptr != nullptr);
+
+  wapp_mem_arena_allocator_destroy(&allocator);
+
+  return wapp_tester_result(result);
+}