Move to GitHub actions (#50)

* Create build.yml

* Delete Jenkinsfile

* Update build.yml

* Update download link

.github/workflows/build.yml

@@ -0,0 +1,54 @@
+name: Build
+
+on:
+  workflow_dispatch:
+  push:
+    paths-ignore:
+      - '.gitignore'
+      - 'LICENSE'
+      - 'README.md'
+
+jobs:
+  build:
+    runs-on: ubuntu-latest
+
+    steps:
+      - name: Checkout repository
+        uses: actions/checkout@v3
+
+      - name: Prepare pack
+        run: bash prepare_pack.sh
+
+      - name: Zip pack
+        run: zip GeyserOptionalPack.mcpack -r . -x ".*" required_files.txt prepare_pack.sh
+
+      - name: Archive artifacts
+        uses: actions/upload-artifact@v3
+        if: success()
+        with:
+          name: GeyserOptionalPack
+          path: GeyserOptionalPack.mcpack
+
+      - name: Publish to Downloads API
+        if: ${{ success() && github.repository == 'GeyserMC/GeyserOptionalPack' && github.ref_name == 'master' }}
+        shell: bash
+        env:
+          DOWNLOADS_USERNAME: ${{ vars.DOWNLOADS_USERNAME }}
+          DOWNLOADS_PRIVATE_KEY: ${{ secrets.DOWNLOADS_PRIVATE_KEY }}
+          DOWNLOADS_SERVER_IP: ${{ secrets.DOWNLOADS_SERVER_IP }}
+        run: |
+          # Save the private key to a file
+          echo "$DOWNLOADS_PRIVATE_KEY" > id_ecdsa
+          chmod 600 id_ecdsa
+          # Set the project
+          project=geyseroptionalpack
+          # Get the version from gradle.properties
+          version=$(cat manifest.json | jq -r '.version | join(".")')
+          # Create the build folder
+          ssh -o StrictHostKeyChecking=no -i id_ecdsa $DOWNLOADS_USERNAME@$DOWNLOADS_SERVER_IP mkdir -p "~/uploads/$project/$GITHUB_RUN_NUMBER/"
+          # Copy over artifacts
+          rsync -P -e "ssh -o StrictHostKeyChecking=no -i id_ecdsa" GeyserOptionalPack.mcpack $DOWNLOADS_USERNAME@$DOWNLOADS_SERVER_IP:~/uploads/$project/$GITHUB_RUN_NUMBER/
+          # Run the build script
+          # Push the metadata
+          echo "{\"project\": \"$project\", \"version\": \"$version\", \"id\": $GITHUB_RUN_NUMBER, \"commit\": \"$GITHUB_SHA\"}" > metadata.json
+          rsync -P -e "ssh -o StrictHostKeyChecking=no -i id_ecdsa" metadata.json $DOWNLOADS_USERNAME@$DOWNLOADS_SERVER_IP:~/uploads/$project/$GITHUB_RUN_NUMBER