feat: add unique handlebar helper

[jainpawan21]

What change does this PR introduce?

1. Add unique handlebar helper and its test.

Why was this change needed?

To remove duplicates in array iteration

Other information (Screenshots)

Usage Example:-

Custom code

{{#each (unique names "name")}}
--<b>{{this}}</b>--- 
{{/each}}

Input:-

{
	"names": [{
		"name": "Name 1",
		"age": "30"
	}, {
		"name": "Name 2"
	}, {
		"name": "Name 1"
	}]
}

HTML output:-

--Name 1----Name 2--

[linear]

NV-2482 unique items in array helper in handlebars

If I send an array with duplicate items in payload and in email (or any other channel) editor, loop through this payload variable, all duplicate items will be considered.

There should be a helper to consider only unique values (take duplicate values only once)

related:- https://stackoverflow.com/a/23733207

David suggested to create process of adding new handlebar helpers easy for community.

[github-actions]

Pull reviewers stats

Stats of the last 30 days for novu:

	User	Total reviews	Time to review	Total comments
	p-fernandez	48	1h 38m	147
	LetItRock	17	17h 33m	65
	djabarovgeorge	16	1d 22h 45m	55
	scopsy	15	24m	3
	ainouzgali	11	53m	50
	unicodeveloper	9	7d 8h 29m	96
	davidsoderberg	5	15h 55m	3
	BiswaViraj	3	1d 22h 30m	2
	jainpawan21	3	4h 46m	2
	peoray	1	27m	1
	michaldziuba03	1	10h 53m	1
	Cliftonz	1	5d 54m	0

[LetItRock]

⭐

[ainouzgali]

@jainpawan21 wdyt of also making it work for unique values of an array of strings?

[ainouzgali]

If the object doesn't have that property we should handle it somehow

[ainouzgali]

If I am getting it right, we will return an array of only the property we filtered the distinct of. I feel we should return the whole object.
For example:
array: [{name:1,var:1},{name:1,var:1},{name:2,var:1}]
should return [{name:1,var:1},{name:2,var:1}]`
instead of ['1','2']

what do you think?