[joss][ui] controls become unusable upon text selection

[anibalsolon]

Part of: openjournals/joss-reviews#6336

when mistakenly selecting the text (and controllers), the sliders stop working.

I'd suggest to apply the following CSS rules to disable text selection on the controllers and re-enabling it to the info panel.

#buttons {
    user-select: none;
}
#info {
    user-select: text;
}
#control {
    user-select: none;
}

[katjaq]

Thank you for the feedback and the improvement fix @anibalsolon . ⭐
We implemented the solution suggested in commit #344f987.