Add helper function for truncating strings with an ellipsis

[carrythebanner]

Use for OpenGraph tag and export to Google Calendar.

[ionous]

you could do something like this if you wanted to avoid that first substr call that goes unused if the length is small enough

{
        if (str.length < maxLength) {
            return str; 
        } else {
          // replace the last character with an ellipsis
           let text = str.substring(0,maxLength-1) + "…";
           return text;
        }
    };

[ionous]

looks good!