Shim ICAL to prevent using the global object

The library ical.js heavily depends on instanceof checks which will break if
two separate versions of the library are used (e.g. bundled one and global
one).

Signed-off-by: Richard Steinmetz <richard@steinmetz.cloud>

webpack.js

@@ -55,7 +55,14 @@ webpackConfig.plugins.push(
 			pattern: './src/assets/iconfont/*.svg'
 		}
 	}),
-	new webpack.IgnorePlugin(/^\.\/locale(s)?$/, /(moment)$/)
+	new webpack.IgnorePlugin(/^\.\/locale(s)?$/, /(moment)$/),
+	new webpack.ProvidePlugin({
+		// Shim ICAL to prevent using the global object (window.ICAL).
+		// The library ical.js heavily depends on instanceof checks which will
+		// break if two separate versions of the library are used (e.g. bundled one
+		// and global one).
+		ICAL: 'ical.js',
+	}),
 )
 
 module.exports = webpackConfig