Add pkl bom module (#1390)

This adds a module that will publish a bom file that will help consumers
align versions for all pkl artifacts using the single bom.

pkl-bom/pkl-bom.gradle.kts

@@ -0,0 +1,60 @@
+/*
+ * Copyright © 2024-2026 Apple Inc. and the Pkl project authors. All rights reserved.
+ *
+ * Licensed under the Apache License, Version 2.0 (the "License");
+ * you may not use this file except in compliance with the License.
+ * You may obtain a copy of the License at
+ *
+ *     https://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+plugins {
+  pklAllProjects
+  `java-platform`
+  `maven-publish`
+  signing
+}
+
+description = "Pkl BOM that includes all modules"
+
+dependencies {
+  constraints {
+    api(projects.pklCli)
+    api(projects.pklCodegenJava)
+    api(projects.pklCodegenKotlin)
+    // Use explicit coordinates for pkl-config-java to avoid ambiguity with fatJar publication
+    api("${project.group}:pkl-config-java:${project.version}")
+    api("${project.group}:pkl-config-java-all:${project.version}")
+    api(projects.pklConfigKotlin)
+    api(projects.pklCore)
+    api(projects.pklDoc)
+    api(projects.pklExecutor)
+    api(projects.pklFormatter)
+    api(projects.pklGradle)
+    api(projects.pklParser)
+    api(projects.pklTools)
+  }
+}
+
+publishing {
+  publications {
+    create<MavenPublication>("library") {
+      from(components["javaPlatform"])
+      pom {
+        url.set("https://github.com/apple/pkl/tree/main/pkl-bom")
+        description.set("Bill of Materials for managing Pkl dependency versions")
+      }
+    }
+  }
+}
+
+configurePklPomMetadata()
+
+configurePomValidation()
+
+configurePklSigning()