Avoid AtomicString implicit conversions for list style type

Add keywords for `type` attribute of <ol> and symbolic predefined
counter style to keywords.json5, and use them.

Note: This CL doesn't add all predefined counter style names because
they are not necessary in many pages.

Bug: 1444094
Change-Id: Ic7eade9074c3b75eb14b91c3241251539b87cb6e
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/4546745


Reviewed-by: Xiaocheng Hu <xiaochengh@chromium.org>
Auto-Submit: Kent Tamura <tkent@chromium.org>
Commit-Queue: Xiaocheng Hu <xiaochengh@chromium.org>
Cr-Commit-Position: refs/heads/main@{#1147427}