build: set the package author

electron-builder warned "author is missed in the package.json" on every run. The
field ends up in installer metadata and, on Linux, the desktop entry's
maintainer.

Name only, taken from the git identity: an email here would be embedded in every
published artifact. The AppImage and Flatpak targets do not require one; deb and
rpm would, if those are ever added.

Co-Authored-By: Claude Opus 5 (1M context) <noreply@anthropic.com>

package.json

@@ -4,6 +4,7 @@
   "version": "1.0.0",
   "description": "Web-based motion graphics editor with keyframing, masking, filters and text animations",
   "license": "MIT",
+  "author": "Kawa",
   "main": "electron/main.js",
   "private": true,
   "scripts": {