[demo]Modify svelte kit for github page

demo/svelte.config.js

@@ -11,6 +11,10 @@ const config = {
 			// 可能因主机而异
 			fallback: 'index.html',
 		}),
+		paths: {
+			// @ts-ignore
+			base: process.argv.includes('dev') ? '' : process.env.BASE_PATH,
+		},
 	},
 	onwarn: (warning, handler) => {
 		if (warning.code.startsWith('a11y-')) {