feat: rebuild heap4 card around upstream FreeRTOS allocator

include/freestanding/stdlib.h

@@ -0,0 +1,4 @@
+#ifndef HEAP4_FREESTANDING_STDLIB_H
+#define HEAP4_FREESTANDING_STDLIB_H
+#include <stddef.h>
+#endif

include/freestanding/string.h

@@ -0,0 +1,7 @@
+#ifndef HEAP4_FREESTANDING_STRING_H
+#define HEAP4_FREESTANDING_STRING_H
+#include <stddef.h>
+void *memcpy(void *destination, const void *source, size_t count);
+void *memset(void *destination, int value, size_t count);
+size_t strlen(const char *text);
+#endif