Vue3 & Webpack generate index.common.js instead of index.js

I have a Vue 3 library. In package.json I have:

"main": "dist/index.js",
"unpkg": "dist/index.umd.min.js",

In vue.config.js I have:

configureWebpack: config => {
   config.output.filename = 'index.js';
},

To build library I do:

vue-cli-service build --target lib --name index src/index.ts && tsc --emitDeclarationOnly --outDir dist -p tsconfig.json

src/index.ts is a file that exports all classes, interfaces etc.

However, when I build my library I have the following in dist:

demo.html  
index.common.js  
index.common.js.map  
index.umd.js  
index.umd.js.map  
index.umd.min.js  
index.umd.min.js.map  
src
tsconfig.tsbuildinfo

As you see there is no index.js but there is index.common.js. Could anyone say how to fix it?