Added support for "Label" components

[SachsKaylee]

Discord nowadays heavily encourages the use of the "Label" component over "ActionRow" in modals. Some components like e.g. selects in modals even requiring their use since they don't have a label of their own.

On the API layer Labels accept their single child in the "component" property instead of "components". I was torn between trying to piggy back on the existing "components" field instead of adding a new one, but ultimately decided that a solution that stays closer to the API will probably be more beneficial in the long run. Very much open to input on this one though.

Thank you for the library!

[jchristgit]

Thank you for the PR (and thank you for adding the since tags, that saves a lot of work for me (: ) I have one small comment but other than that it looks good to me.

[SachsKaylee]

I'll just biggy back on this open PR. Im not sure if Discord changed their API validation just today, because I didnt have this exact issue yesterday, but Component.TextInput has an empty string as its default for label. However, when a component inside a label has a non-nil value for its own label (empty strings aren't allowed apparently, I didnt run into that issue when testing) the API validation rejects it. - so this weird workaround is required for that:

text_input =
  Component.TextInput.text_input(
   # The "nil" here gets ignored, I think the new() function skips over nil values.
    nil,
    field_id_str,
    field_opts
  )

%Component{text_input | label: nil}

[jchristgit]

Could we change the default to just be an empty string or does that cause other issues then?

[SachsKaylee]

The default for Component.TextInput is currently an empty string, which causes the problem.

A text input inside of a label component must have null or nothing at all as their label-field at the API level. However, the current validation on Nostrum side prevents us passing anything but a string to the API.

[drozdzynski]

Hello guys any updates with this pull request? 😄