Build from source: missing dist directory

I think the build file makes certain assumptions about the existing directory structure. If you want to keep `/dist` out of git history, you'll need to handle the directory existing/absent.

This was my solution in my fork:
```js
vue({
css(style) {
const file = require.resolve("vue-resize/dist/vue-resize.css");
style += fs.readFileSync(file, { encoding: "utf8" });

try {
fs.statSync("dist");
} catch (_) {
fs.mkdirSync("dist");
}

fs.writeFileSync(
"dist/vue-virtual-scroller.css",
new CleanCSS().minify(style).styles
);
},
});
```