Update jimp requirement from ^0.6.4 to ^0.7.0 in /app

Updates the requirements on [jimp](https://github.com/oliver-moran/jimp) to permit the latest version.
- [Release notes](https://github.com/oliver-moran/jimp/releases)
- [Changelog](https://github.com/oliver-moran/jimp/blob/master/CHANGELOG.md)
- [Commits](https://github.com/oliver-moran/jimp/compare/v0.6.4...v0.7.0)

Signed-off-by: dependabot-preview[bot] <support@dependabot.com>

app/package.json

@@ -51,7 +51,7 @@
   "dependencies": {
     "@fortawesome/fontawesome-free": "^5.10.1",
     "electron-dl": "^1.14.0",
-    "jimp": "^0.6.4",
+    "jimp": "^0.7.0",
     "jquery": "^3.4.1",
     "jquery-ui-dist": "^1.12.1",
     "json5": "^2.1.0",