sideways: writing-mode accepts `sideways-rl` and `sideways-lr`

* Add `sideways-rl` and `sideways-lr` to the `writing-mode` entry of
  css_properties.json5.

* The ComputedStyle field size for `writing-mode` is increased by 1 bit.
  It increases sizeof(ComputedStyle).

* CSS parser accepts them only if the runtime flag is enabled.

* Typed CSSOM accepts them only if the runtime flag is enabled.

This CL has no behavior changes in production due to a disabled
runtime flag.

Bug: 40501131
Change-Id: I10302dc0ad90a2b38e80937be78b1f8094c3ca46
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/5645089
Reviewed-by: Rune Lillesveen <futhark@chromium.org>
Commit-Queue: Rune Lillesveen <futhark@chromium.org>
Auto-Submit: Kent Tamura <tkent@chromium.org>
Cr-Commit-Position: refs/heads/main@{#1318534}