i.icon {
    display: inline-block;
    width: 12px;
    height: 12px;
    background-position: center;
    background-size: contain;
    vertical-align: middle;
    margin-right: 5px;
}

i.icon.mastodon {
    background-image: url(../media/icons/mastodon.svg);
}

i.icon.matrix {
    background-image: url(../media/icons/matrix.svg);
}