fix: set RESOURCES_PATH relative to app.getAppPath() (#2064)

When running the app with system electron, process.resourcesPath points
to the resources folder of the system electron, not the one from
feishin.

src/main/index.ts

@@ -335,7 +335,7 @@ if (isDevelopment) {
 }
 
 const RESOURCES_PATH = app.isPackaged
-    ? path.join(process.resourcesPath, 'assets')
+    ? path.join(path.dirname(app.getAppPath()), 'assets')
     : path.join(__dirname, '../../assets');
 
 const getAssetPath = (...paths: string[]): string => {