Enhancement: allow for string content fields with multiple values

[landure]

I'm using Hugo site generator. Hugo allow for Aliases.

The definition of the aliases front matter field should be:

				{
					"title": "Aliases",
					"name": "aliases",
					"type": "string",
					"single": true,
					"multiple": true
				},

But the "multiple" option is not valid for string fields.

The solution is to allow for "multiple" option to work for string fields, as it does for images.

[estruyf]

It might be better to have an option for a free text choice field.

[estruyf]

It made more sense to have a new list field.

Available for testing in the latest beta

[estruyf]

The configuration of the list field looks as follows:

{
  "title": "Alias",
  "name": "alias",
  "type": "list"
}