Update schema with new 'noindex' document attribute

[TylerZeroMaster]

part of openstax/ce#2240

Update schema to allow noindex attribute on document

[TylerZeroMaster]

noindex attribute is optional

GIVEN

• A book repository
• Version editor-0.0.0-dev-200 POET

  WHEN

• A document element does not have a noindex attribute

  THEN

• There are no validation errors

---

noindex attribute only supports values true and false

GIVEN

• A book repository
• Version editor-0.0.0-dev-200 POET

  WHEN

• The noindex attribute is added to the document element in a module
• The value of the attribute is set to anything other than "true" or "false" (Known issue: whitespace is ignored during validation so values like "true " will also be valid)

  THEN

• There are no validation errors related to xml schema

---

noindex attribute is only supported on document element

GIVEN

• A book repository
• Version editor-0.0.0-dev-200 POET

  WHEN

• The noindex attribute is added to anything other than a document element with a value of "true" or "false"

  THEN

• There are validation errors related to xml schema

[omehes]

all tests passed. looks good with the dev extension provided

[omehes]

verified in poet ext. 7.0.0