feat(ApplicationCommand): add #equals

[ckohen]

Please describe the changes this PR makes and why it should be merged:

Adds ApplicationCommand#equals since checking the equivalence of application commands is a non-trivial task. Especially when handling the instantiated class and raw data.

Oh, and also because @IanMitchell asked for it

Status and versioning classification:

• Code changes have been tested against the Discord API, or there are no code changes
• I know how to update typings and have done so, or typings don't need updating
• This PR changes the library's interface (methods or parameters added)

Stale

[ImRodry]

You don't actually need the ?? 0 because you'd be comparing undefined to undefined if neither one of the commands have options, which is still valid and produces the same output

[ckohen]

this.options always exists currently, the ?. on the RHS is misleading. I could remove the one on the RHS only but this is accounting for the (yes unlikely) case that someone changed that property in runtime

[ImRodry]

They can also provide an object that they construct in which case it won't have options so it's good to keep both ?. there, just saying that because of your TODO comment, since you can easily remove those

[kyranet]

We really need unit tests for this, but looks good to me.

[ImRodry]

I strongly disagree with the need for an option here and specially it being set to false by default. Option order is something that will change how Discord handles your commands so if you really want that option it should default to true. The best in my opinion would be to default to true and remove that option.
Also why do you still have TODO comments?

[ckohen]

I have TODO comments because they're TODO for v14, not for now.

As for your disagreement. No, order doesn't change how discord handles your commands, it changes how it is stored on the API. As I've already said, the client does not strictly respect this order and the info blocks I added for those parameters clearly indicates the thought process for that.

[ImRodry]

I have TODO comments because they're TODO for v14, not for now.

As for your disagreement. No, order doesn't change how discord handles your commands, it changes how it is stored on the API. As I've already said, the client does not strictly respect this order and the info blocks I added for those parameters clearly indicates the thought process for that.

The client may not strictly respect that order, but it does to some extent. So if you change the order of an option or a subcommand even, the client will display it differently, which is why I think it should at least default to true.
As for the TODO comments, why are they for v14?