Make grpc-web available on bazel central registry

grpc-web needs to be listed in the Bazel Central Registry to be available to bzlmod users. (Users can currently work around this by using archive_override, I believe.)

Steps required:

[ ] Make release archives stable. See https://github.com/grpc/grpc-web/pull/1464
[ ] Submit a PR to the Bazel Central Registry per https://github.com/bazelbuild/bazel-central-registry/blob/main/docs/README.md. In progress: https://github.com/bazelbuild/bazel-central-registry/pull/2541

grpc / grpc-web

Make grpc-web available on bazel central registry #1465