Add github workflow

.github/workflows/build.yml

@@ -0,0 +1,59 @@
+name: Build
+
+on:
+  workflow_dispatch:
+  push:
+    tags:
+      - '*'
+
+env:
+  # For any reason, specifying this in the modrinth step does not work?
+  # But it is also well documented here, so this should be ok to do
+  MODRINTH_TOKEN: ${{ secrets.MODRINTH_TOKEN }}
+
+jobs:
+  build:
+    runs-on: ubuntu-latest
+    steps:
+      - name: Check tag condition
+        if: startsWith(github.ref, 'refs/tags/')
+        run: echo "Ref is a tag"
+
+      - name: Check out project
+        if: success()
+        uses: actions/checkout@v3
+
+      - name: Set up JDK 17
+        if: success()
+        uses: actions/setup-java@v3
+        with:
+          java-version: 17
+          distribution: 'microsoft'
+
+      - name: Setup Gradle
+        if: success()
+        uses: gradle/gradle-build-action@v2
+        with:
+          gradle-version: 7.4.2
+
+      - name: Build
+        if: success()
+        run: gradle remapJar
+
+      - name: Release on GitHub
+        if: success() && startsWith(github.ref, 'refs/tags/') # Failsafe check again
+        uses: softprops/action-gh-release@v1
+        with:
+          files: |
+            **/libs/server-portals-*.jar
+            README.md
+            CHANGELOG.md
+            LICENSE
+          body_path: CHANGELOG.md
+          draft: false
+          prerelease: false
+          fail_on_unmatched_files: true
+
+      - name: Upload to modrinth
+        if: success()
+        run: gradle modrinth