Use automatic version when building snap directly

Make it easier to build a snap from your working copy by removing the
restriction of having to modify the version field first.

.github/workflows/deploy.yml

@@ -58,7 +58,7 @@ jobs:
       - run: |
           VERSION=$(grep '"version"' package.json | cut -d '"' -f 4)
           echo $VERSION
-          sed -i "s/@VERSION@/$VERSION/g" snap/snapcraft.yaml
+          sed -i "s/^version:.*/version: '$VERSION'/" snap/snapcraft.yaml
       - uses: snapcore/action-build@v1
         id: snapcraft
       - uses: actions/upload-artifact@v2