CrOS Settings: Create shared stylesheet for storybook pages

Bug: b:345815612
Change-Id: I09cc5f75320d040f54c3c5ccc5167bd3b640077f
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/5619850


Reviewed-by: Connie Xu <conniekxu@chromium.org>
Commit-Queue: Wes Okuhara <wesokuhara@google.com>
Cr-Commit-Position: refs/heads/main@{#1313704}