Chrome and Firefox ignore embolden assignment.

[dumol]

"Varela Round" is closer to "Arial Rounded MT Bold" if embolden is used, but this trick only works on WebKitGTK:

    <match target="pattern">
        <test qual="any" name="family">
            <string>Arial Rounded MT Bold</string>
        </test>
        <edit name="family" mode="assign" binding="strong">
            <string>Varela Round</string>
        </edit>
        <edit name="embolden" mode="assign">
            <bool>true</bool>
        </edit>
    </match>