Add dependabot to AUTHORS file

To allow changes like this: https://skia-review.googlesource.com/c/skia/+/625016

Bug: skia:14018
Change-Id: I7cea93633501c5336d01a5461daa62275d10ff5e
Reviewed-on: https://skia-review.googlesource.com/c/skia/+/629631
Commit-Queue: Ravi Mistry <rmistry@google.com>
Reviewed-by: Joe Gregorio <jcgregorio@google.com>
1 file changed