Version 0.3.1

Update versions.
Add versioned browsers bzl file.

Add the following to your WORSKPACE file to use:

load("@bazel_tools//tools/build_defs/repo:http.bzl", "http_archive")

http_archive(
    name = "io_bazel_rules_webtesting",
    sha256 = "f89ca8e91ac53b3c61da356c685bf03e927f23b97b086cc593db8edc088c143f",
    urls = [
        "https://github.com/bazelbuild/rules_webtesting/releases/download/0.3.1/rules_webtesting.tar.gz",
    ],
)

load("@io_bazel_rules_webtesting//web:repositories.bzl", "web_test_repositories")

web_test_repositories()