Add github action to publish TripleA client Jar file

The jar file will in turn be used as a dependency for other
repositories, specifically things like the lobby.

.github/workflows/publish-jar-file.yml

@@ -0,0 +1,33 @@
+# Jar file is useful for server code, so that the server code can depend on
+# the TripleA client code (jar file). The TripleA client should include
+# the 'http client' (AKA REST API) code for communicating with server
+name: Publish Jar File
+on:
+  push:
+    branches:
+      - master
+env:
+  GITHUB_TOKEN: ${{ secrets.GITHUB_TOKEN }}
+jobs:
+  build:
+    runs-on: Ubuntu-20.04
+    steps:
+      - name: Checkout code
+        uses: actions/checkout@v4
+#        with:
+#          # Fetch depth of 0 is needed so we checkout the full revision history
+#          # The current revision count will be used as our build-number
+#          fetch-depth: '0'
+      - name: Set up JDK 11
+        uses: actions/setup-java@v4
+        with:
+          distribution: temurin
+          java-version: 11
+      - name: set build version variables
+        run: |
+          BUILD_VERSION=$(game-app/run/.build/get-build-version)
+          echo "JAR_VERSION=$BUILD_VERSION" | tee -a $GITHUB_ENV
+      - name: Publish package
+        run: ./gradlew :game-app:game-headed:publish
+        env:
+          GITHUB_TOKEN: ${{ secrets.GITHUB_TOKEN }}

game-app/game-headed/build.gradle

@@ -7,6 +7,7 @@ plugins {
 
 archivesBaseName = "$group-$name"
 mainClassName = "org.triplea.game.client.HeadedGameRunner"
+version = System.getenv("JAR_VERSION")
 
 ext {
     releasesDir = file("$buildDir/releases")
@@ -43,6 +44,24 @@ jar {
     }
 }
 
+publishing {
+    repositories {
+        maven {
+            name = "GitHubPackages"
+            url = uri("https://maven.pkg.github.com/triplea-game/triplea")
+            credentials {
+                username = System.getenv("GITHUB_ACTOR")
+                password = System.getenv("GITHUB_TOKEN")
+            }
+        }
+    }
+    publications {
+        shadow(MavenPublication) { publication ->
+            project.shadow.component(publication)
+        }
+    }
+}
+
 clean.doFirst {
   delete "$projectDir/.assets/"
   delete "$projectDir/assets/"