CSS custom properties bug using v-bind

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Reason

The first paint will not contain styles that have used v-bind. Due to @vue/server-renderer outputting non-valid CSS custom properties

How reproduce

There might be a need to inspect the output in view-source:http://localhost:3000/ due to the initial hydration fixing the issue

This minimum reproducible example requires a server side rendered app. To run the app run the command npm start

This will produce a server-side app running on ``` http://localhost:3000 ````

You should then be able to see the inline styled v-bind variables having an invalid syntax

<div id="app">
    <div class="fancy-styling" style="7ba5bd90-fancy-theme_width:250px;7ba5bd90-fancy-theme_height:250px;7ba5bd90-fancy-theme_background-color:green;">
        <h1>Hallo world</h1>
    </div>
</div>

The CSS custom properties that are dynamically generated does not contain the required -- prefix

A valid property would look like. --7ba5bd90-fancy-theme_width:250px instead of the current 7ba5bd90-fancy-theme_width:250px