workspace: add buildifier

To run: `bazel run //:buildifier`

To be done: document and automate

Change-Id: I7631e45915d61d2b95b0d8b0d893d0e1de2ccbed
Reviewed-on: https://gerrit.hackerspace.pl/c/hscloud/+/1847
Reviewed-by: palid <palid@hackerspace.pl>

BUILD

@@ -27,3 +27,8 @@ config_setting(
     constraint_values = ["@bazel_tools//platforms:linux"],
     visibility = ["//visibility:public"],
 )
+
+load("@com_github_bazelbuild_buildtools//buildifier:def.bzl", "buildifier")
+buildifier(
+    name = "buildifier",
+)

WORKSPACE

@@ -297,3 +297,13 @@ http_file(
 # viz.js 2.x used by //dc/topo
 load("//third_party:vizjs.bzl", "vizjs_repositories")
 vizjs_repositories()
+
+# buildifier and friends
+http_archive(
+    name = "com_github_bazelbuild_buildtools",
+    sha256 = "ae34c344514e08c23e90da0e2d6cb700fcd28e80c02e23e4d5715dddcb42f7b3",
+    strip_prefix = "buildtools-4.2.2",
+    urls = [
+        "https://github.com/bazelbuild/buildtools/archive/refs/tags/4.2.2.tar.gz",
+    ],
+)