Add fragment links only on docs pages
Add fragment links only on docs pages

Add fragment links only on docs pages and only when there is an 'id'
attribute.

google/gvisor-website,google/gvisor,google/gvisor-website,google/gvisor,google/gvisor,google/gvisor,google/gvisor,google/gvisor,google/gvisor,google/gvisor