docs: Update README and add CI build workflow

Author: CriticalRange

.github/workflows/build.yml

@@ -0,0 +1,30 @@
+name: Build Catalyst
+
+on:
+  push:
+    branches: [ "main" ]
+  pull_request:
+    branches: [ "main" ]
+
+permissions:
+  contents: read
+
+jobs:
+  build:
+    runs-on: ubuntu-latest
+    steps:
+    - uses: actions/checkout@v4
+    
+    - name: Set up JDK 21
+      uses: actions/setup-java@v4
+      with:
+        java-version: '21'
+        distribution: 'temurin'
+        
+    - name: Setup Gradle
+      uses: gradle/actions/setup-gradle@v3
+      
+    - name: Build with Gradle
+      # Note: This will fail if HytaleServer.jar is missing. 
+      # You may need to provide it via a custom mechanism or mock it.
+      run: ./gradlew build