Access named ranges from a spreadSheet not from a sheet.

[lavigne958]

Is your feature request related to a problem? Please describe.
NamedRanges are not tight to a particular sheet object, one could create a function that returns a list of Cell objects
obtained from only a given namedRange access via an instance of SpreadSheet without having to first get any WorkSheet.

Describe the solution you'd like
Create a new function (likely named namedRange) to get the content of a namedRange

Describe alternatives you've considered
get the first sheet and then get the namedRange, regardless if it is located on the first sheet ot not.

Additional context
From the API v4: only the spreadSheetID and the namedRange name is required to obtain the content
https://developers.google.com/sheets/api/reference/rest/v4/spreadsheets.values/get