implement basic github action comment reporting target diffs (#9022)

This is missing logic:
- report average
- don't bother reporting if the results are negligeable
- praise the user if it's improving the situation
- shame the user if it's not improving the situation

.github/workflows/build_firmware.yml

@@ -21,7 +21,7 @@ jobs:
     # Use 'arctastic' self-hosted runner pool when building in the main repo
     runs-on: ${{ github.repository_owner == 'meshtastic' && 'arctastic' || 'ubuntu-latest' }}
     outputs:
-      artifact-id: ${{ steps.upload.outputs.artifact-id }}
+      artifact-id: ${{ steps.upload-firmware.outputs.artifact-id }}
     steps:
       - uses: actions/checkout@v6
         with:
@@ -71,7 +71,7 @@ jobs:
 
       - name: Store binaries as an artifact
         uses: actions/upload-artifact@v6
-        id: upload
+        id: upload-firmware
         with:
           name: firmware-${{ inputs.platform }}-${{ inputs.pio_env }}-${{ inputs.version }}
           overwrite: true
@@ -84,3 +84,12 @@ jobs:
             release/*.zip
             release/device-*.sh
             release/device-*.bat
+
+      - name: Store manifests as an artifact
+        uses: actions/upload-artifact@v6
+        id: upload-manifest
+        with:
+          name: manifest-${{ inputs.platform }}-${{ inputs.pio_env }}-${{ inputs.version }}
+          overwrite: true
+          path: |
+            release/*.mt.json