bzlmod: Set up automated BCR releases (#1350)

This uses the https://github.com/bazel-contrib/publish-to-bcr app.

.bcr/config.yml

@@ -0,0 +1 @@
+fixedReleaser: fmeum

.bcr/metadata.template.json

@@ -0,0 +1,12 @@
+{
+  "homepage": "https://github.com/bazelbuild/bazel-gazelle",
+  "maintainers": [
+    {
+      "email": "fabian@meumertzhe.im",
+      "github": "fmeum",
+      "name": "Fabian Meumertzheim"
+    }
+  ],
+  "versions": [],
+  "yanked_versions": {}
+}

.bcr/presubmit.yml

@@ -0,0 +1,18 @@
+bcr_test_module:
+  module_path: tests/bcr
+  matrix:
+    platform:
+    - centos7
+    - debian10
+    - ubuntu2004
+    - macos
+    - windows
+  tasks:
+    run_test_module:
+      name: Run test module
+      platform: ${{ platform }}
+      build_targets:
+      - //...
+      - //:gazelle
+      test_targets:
+      - //...

.bcr/source.template.json

@@ -0,0 +1,4 @@
+{
+  "integrity": "",
+  "url": "https://github.com/{OWNER}/{REPO}/releases/download/{TAG}/{REPO}-{TAG}.tar.gz"
+}

BUILD.bazel

@@ -6,6 +6,7 @@ load("//:def.bzl", "gazelle", "gazelle_binary")
 # gazelle:exclude vendor
 # gazelle:exclude third_party
 # gazelle:exclude .bazelci
+# gazelle:exclude .bcr
 # gazelle:exclude .idea
 # gazelle:exclude .github
 # gazelle:exclude .vscode