Add Support For Timeframe Units With Zero Delta in Icelandic Locale

[anishnya]

Feature Request

Currently we do not have timeframe strings in the Icelandic locale that correspond with a time delta of zero. For example, we do not have a string that represents "0 seconds" in the Icelandic locale. We would like to fix this. For the time being, since we don't cover this case within the Icelandic locale, I think we'll resort to any time delta of 0 corresponding to the future tense of strings.