Remove references to Firefox. Remove link to a four year old roadmap.
Fix the placeholder mailing-list link to point at our project.
Change-Id: Iaacb8e077dd9316fc305f255a456133ce0fae25d
Reviewed-on: https://skia-review.googlesource.com/c/skia/+/491451
Reviewed-by: Heather Miller <hcm@google.com>
Reviewed-by: Joe Gregorio <jcgregorio@google.com>
Commit-Queue: Brian Osman <brianosman@google.com>