Swiftlint: Rule Request: Use .first instead of [0]

[72A12F4E]

Rule Request

1. Why should this rule be added? Share links to existing discussion about what
   the community thinks about this.

Indexing a collection using [0] is unsafe and could cause a crash if the collection is empty

1. Provide several examples of what _would_ and _wouldn't_ trigger violations.

Bad

let value = array[0]
let something = resource.collection[0].group.value

Good

let value = array.first
let something = resource.collection.first.group.value

1. Should the rule be configurable, if so what parameters should be configurable?

No

1. Should the rule be opt-in or enabled by default? Why?

I think this rule should be enabled by default for the index-at-zero case. If the rule is expanded beyond that, I think it should be opt-in.

[marcelofabri]

This should be opt-in if implemented.