Duration binding helper

[mike12345567]

Description

Quick addition of a duration helper which can be used to create relative humanized date strings. This comes from a question on Discord where they wanted to recreate the following JS function in Budibase:

var eventTime = '1366549200';
var currentTime = '1366547400';
//Now i am passing the left time from controller itself which handles timezone stuff (UTC), just to simply question i used
//harcoded values.
var leftTime = eventTime - currentTime;
var duration = moment.duration(leftTime, 'seconds');
var interval = 1000;

This helper makes this possible (and arguably easier!) as such:

{{duration ( subtract (date currentTime "X")(date eventTime "X")) "seconds"}}

This was a great use case for making sure the helpers system is very easily extensible - this also uncovered some features that were missing from our main date formatter after the transition from moment -> dayjs (dayjs by default is quite light weight, needs extensions).

[shogunpurple]

Nice - LGTM!