Add ulan@ to owners of src/libplatform

Change-Id: I328dde4ef8265fa15e2dfc7ac689e175465edebd
Reviewed-on: https://chromium-review.googlesource.com/c/v8/v8/+/2366700Reviewed-by: Michael Lippautz <mlippautz@chromium.org>
Commit-Queue: Ulan Degenbaev <ulan@chromium.org>
Cr-Commit-Position: refs/heads/master@{#69503}

src/libplatform/OWNERS

 mlippautz@chromium.org
+ulan@chromium.org
 
 # COMPONENT: Blink>JavaScript>API