fix bookmaker typo

Fix one character and update the web documentation.

Docs-Preview: https://skia.org/?cl=128938
TBR=robertphillips@google.com
Bug: skia:6898
Change-Id: I4525ef8d3bae85ef1d63f84ff414a32b9935ae0e
Reviewed-on: https://skia-review.googlesource.com/128938
Reviewed-by: Cary Clark <caryclark@skia.org>
Commit-Queue: Cary Clark <caryclark@skia.org>
Auto-Submit: Cary Clark <caryclark@skia.org>
3 files changed