Add github actions

.github/workflows/build.yml

@@ -0,0 +1,26 @@
+name: Build
+on:
+    - push
+    - pull_request
+
+jobs:
+    build:
+        name: Test
+        runs-on: ubuntu-latest
+        steps:
+            - uses: actions/checkout@v3
+              name: Checkout repository
+            - name: Set up JDK 17
+              uses: actions/setup-java@v3
+              with:
+                  distribution: temurin
+                  java-version: 17
+            - name: Set up gradle cache
+              uses: gradle/gradle-build-action@v2
+            - name: Build with gradle
+              run: ./gradlew clean test remapJar --stacktrace
+            - name: Upload build artifact
+              uses: actions/upload-artifact@v3
+              with:
+                  path: build/libs/Firmament-*.jar
+