Update main.yml

Fix: Node.js 12 actions are deprecated.

.github/workflows/main.yml

@@ -5,9 +5,9 @@ jobs:
     name: Build
     runs-on: ubuntu-latest
     steps:
-      - uses: actions/checkout@v2
+      - uses: actions/checkout@v3
       - name: Set up python
-        uses: actions/setup-python@v2
+        uses: actions/setup-python@v3
         with:
           python-version: '3.x'
           architecture: 'x64'
@@ -16,7 +16,7 @@ jobs:
       - name: Build firmware
         run: platformio run
       - name: Archive
-        uses: actions/upload-artifact@v2
+        uses: actions/upload-artifact@v3
         with:
           name: firmware.bin
           path: .pio/build/*/firmware.bin