bulma: message edition + extra menu + improvments: - add an extra menu template with `Edit` and `Quote` - add a template for previous editions popup - fix `own_msg` class application - add CSS for edit mode - cosmetic changes

#body {
    display: flex;
    align-items: center;
    justify-content: center;
}

#link_section {
    font-weight: bold;
    text-align: center;
    font-size: 1.5rem;
}

article p:last-child {
    text-align: center;
}