Upgrades Bazel to 4.2.0, rules_nodejs and @bazel/* packages to …

…`4.0.0`, and NodeJS to `12.22.5`.

These are the latest Bazel and `rules_nodejs` versions, necessary to include some fixes/improvements for re-exporting `js_library()` and `ts_library()` targets, see #39 (comment).

`rules_nodejs@4.0.0` actually updates NodeJS to `14.17.5`, however this breaks `@bazel/postcss@0.5.0` and there is no later release for it. There is actually a fix, but it hasn't been released. I filed bazelbuild/rules_postcss#73 to request a release, but for now I'm keeping NodeJS at `12.22.5`, which is the current latest release that does not include the v14 breaking change. Note that NodeJS v13 is already unsupported as it is not an LTS release.

This is the most I can upgrade Bazel/`rules_nodejs` without breaking `@bazel/postcss`.

.bazelversion

@@ -1,2 +1 @@
-3.0.0
-
+4.2.0

WORKSPACE.bazel

@@ -15,13 +15,14 @@ workspace(
 load("@bazel_tools//tools/build_defs/repo:http.bzl", "http_archive")
 http_archive(
     name = "build_bazel_rules_nodejs",
-    sha256 = "6142e9586162b179fdd570a55e50d1332e7d9c030efd853453438d607569721d",
-    urls = ["https://github.com/bazelbuild/rules_nodejs/releases/download/3.0.0/rules_nodejs-3.0.0.tar.gz"],
+    sha256 = "8a7c981217239085f78acc9898a1f7ba99af887c1996ceb3b4504655383a2c3c",
+    urls = ["https://github.com/bazelbuild/rules_nodejs/releases/download/4.0.0/rules_nodejs-4.0.0.tar.gz"],
 )
 
 # The npm_install rule runs yarn anytime the package.json or package-lock.json file changes.
 # It also extracts any Bazel rules distributed in an npm package.
-load("@build_bazel_rules_nodejs//:index.bzl", "npm_install")
+load("@build_bazel_rules_nodejs//:index.bzl", "node_repositories", "npm_install")
+node_repositories(node_version = "12.22.5")
 npm_install(
     # Name this npm so that Bazel Label references look like @npm//package
     name = "npm",