Add auto build workflow (#1)

* Add epic new workflow

* Ignore repo files in output

* Hopefully reduce double zipping

* I guess double zipping is inevitable

.github/workflows/build.yml

@@ -0,0 +1,30 @@
+name: build-modpack
+
+on: [push]
+
+jobs:
+  build-pack:
+    name: Use packwiz to build the curseforge pack
+    runs-on: ubuntu-latest
+
+    steps:
+
+      - name: Checkout Repo
+        uses: actions/checkout@v4
+      
+      - name: Setup Go environment
+        uses: actions/setup-go@v5.0.0
+        with: 
+          go-version: '>=1.19.0'
+      
+      - name: Install Packwiz
+        run: |
+          go install github.com/packwiz/packwiz@latest
+
+      - name: Build pack
+        run: packwiz curseforge export
+      
+      - name: Upload pack to actions
+        uses: actions/upload-artifact@v3
+        with:
+          path: GregTech CEu Modern Community Pack-*.zip