Switch to GitHub actions

Signed-off-by: Tomas Slusny <slusnucky@gmail.com>

.github/workflows/CI.yml

@@ -0,0 +1,32 @@
+name: CI
+
+on: [ push, pull_request ]
+
+jobs:
+  build:
+    runs-on: ubuntu-20.04
+
+    steps:
+      - name: Checkout
+        uses: actions/checkout@v2
+
+      - name: Cache
+        uses: actions/cache@v2
+        with:
+          path: |
+            ~/.m2/repository
+            ~/.cache/runelite
+          key: ${{ runner.os }}-cache-${{ hashFiles('**/pom.xml', '**/build.sh') }}
+          restore-keys: |
+            ${{ runner.os }}-cache-
+
+      - name: Set up JDK 11
+        uses: actions/setup-java@v1
+        with:
+          java-version: 11
+
+      - name: Build
+        run: ./ci/build.sh
+
+      - name: Remove build artifacts
+        run: rm -rf ~/.m2/repository/net/runelite