How to set encoding to utf-8 on a IIS web.config file?

I have this

<?xml version="1.0" encoding="UTF-8"?>

<configuration>

    <appSettings>
        <add key="ContentServer" value="true" />
    </appSettings>
    <connectionStrings />

    <system.web>
        <trace enabled="false" requestLimit="25" pageOutput="false" traceMode="SortByTime" localOnly="false" />
        <customErrors mode="Off" />
        <compilation debug="false" />
        <authentication mode="Windows" />
    </system.web>
</configuration>

How do I set the encoding to utf-8 for files sent to client. Actually There can be other types of files sent to clients like js,css,images. But I have aspx pages, that I want to set text/html; charset=utf-8" content-type to. How can I add this to this web.config code?

Thanks