chore: add patch description to gin allocator patch (#26415)

patches/chromium/export_gin_v8platform_pageallocator_for_usage_outside_of_the_gin.patch

@@ -4,6 +4,10 @@ Date: Tue, 3 Nov 2020 16:49:32 -0800
 Subject: export gin::V8Platform::PageAllocator for usage outside of the gin
  platform
 
+In order for memory allocation in the main process node environment to be
+correctly tagged with MAP_JIT we need to use gins page allocator instead
+of the default V8 allocator.  This probably can't be usptreamed.
+
 diff --git a/gin/public/v8_platform.h b/gin/public/v8_platform.h
 index da2aeb2f2da84fe47d5cc7d721f8d3dade0c0972..4ddad9065782fad5927bc0481ad772014af0d689 100644
 --- a/gin/public/v8_platform.h