Use bzlmod to manage external dependencies (#186)

* Use bzlmod to manage external dependencies

Bzlmod is the new way to to manage external dependencies. The
`--enable_bzlmod` flag was introduced in Bazel 6 and has been turned on
by default since Bazel 7, so declaring external dependencies in
`WORKSPACE` is considered leagcy behavior. The old `WORKSPACE`-system is
planned to be disabled in Bazel 8 and to be removed altogether in Bazel
9.

This commit migrates from `WORKSPACE` to bzlmod.

References:

- https://bazel.build/external/overview
- https://bazel.build/external/migration
- https://blog.bazel.build/2023/12/11/bazel-7-release.html#bzlmod

* Remove lockfile MODULE.bazel.lock

Author: luangong

MODULE.bazel

@@ -0,0 +1,4 @@
+module(name = "protobuf_javascript", version = "3.21.2")
+
+bazel_dep(name = "protobuf", version = "21.7", repo_name = "com_google_protobuf")
+bazel_dep(name = "rules_pkg", version = "0.9.1")

WORKSPACE.bzlmod

@@ -0,0 +1,2 @@
+# When Bzlmod is enabled, this file replaces the content of the original WORKSPACE and
+# makes sure no WORKSPACE prefix or suffix are added when Bzlmod is enabled.