Fix asset path in build

vite.config.js

@@ -2,6 +2,7 @@ const { defineConfig } = require("vite")
 import fs from "fs"
 const allHtmlFiles = fs.readdirSync(".").filter((f) => f.endsWith(".html"))
 const input = {}
+const ASSET_URL = process.env.ASSET_URL || ""
 
 for (const html of allHtmlFiles) {
   const name = html.substring(0, html.length - 5)
@@ -14,6 +15,7 @@ module.exports = defineConfig({
       input,
     },
   },
+  base: `${ASSET_URL}`,
   server: {
     port: 1234,
   },