Update CI to checkout@v4, upload-artifact@v4 (#38)

Author: tupaschoal

.github/workflows/ci.yml

@@ -4,7 +4,7 @@ jobs:
   build:
     runs-on: ubuntu-latest
     steps:
-    - uses: actions/checkout@v2
+    - uses: actions/checkout@v4
     - name: Download gxc
       run: |
         curl -Lo tools.tar.gz https://github.com/IntelOrca/libsawyer/releases/download/v1.1.0/libsawyer-tools-linux-x64.tar.gz
@@ -14,7 +14,7 @@ jobs:
     - name: Create graphics asset pack
       run: node build.mjs --verbose
     - name: Upload artifacts
-      uses: actions/upload-artifact@v2
+      uses: actions/upload-artifact@v4
       with:
         name: "OpenRCT2 Open Graphics Asset Pack"
         path: out/**/*