New labels

Can you please add the following labels / descriptions?

LOW_SIGNIF_PRELIM_SENT: A low-significance preliminary GCN has been sent.

SIGNIF_LOCKED: The GraceID associated with this event has all annotations required for an alert, passes the significant public alert threshold, and will only be automatically updated when preliminary alerts are sent.

LOW_SIGNIF_LOCKED: The GraceID associated with this event has all annotations required for an alert, passes the low-significance public alert threshold, and will only be automatically updated when preliminary alerts are sent.

Color wise, let's make LOW_SIGNIF_LOCKED green and the other two black (this matches the style that the others follow where the green labels appear more commonly and are needed for black labels like GCN_PRELIM_SENT.