3506037: Add help elements.

Closes #3506037

graphql/webform.base.graphqls

+scalar WebformSubmissionFileUpload
+scalar WebformSubmissionValue
+
+type Mutation {
+  submitWebform(
+    id: String!
+    elements: [WebformSubmissionElement]
+    files: [WebformSubmissionFile]
+    sourceEntityId: String
+    sourceEntityType: String
+  ): WebformSubmissionResult!
+}
+
+type Webform {
+  id: String!
+  title: String!
+  elements: [WebformElement]
+}
+
+type WebformSubmissionResult {
+  errors: [String]
+  validationErrors: [WebformSubmissionValidationError]
+  submission: WebformSubmission
+}
+
+type WebformSubmission {
+  id: Int!
+  uuid: String!
+  token: String!
+  webform: Webform!
+  sourceEntityType: String
+  sourceEntityId: String
+}
+
+type WebformSubmissionValidationError {
+  """
+  The ID of the webform element for which the validation errors occurred.
+  """
+  element: String
+  """
+  The validation error messages.
+  """
+  messages: [String]
+}
+
+input WebformSubmissionElement {
+  """
+  The name of the webform element.
+  """
+  element: String!
+
+  """
+  The value. Can be anything that is consumable by form API submission.
+  """
+  value: WebformSubmissionValue!
+}
+
+input WebformSubmissionFile {
+  """
+  The name of the webform element.
+  """
+  element: String!
+
+  """
+  The file to upload. This is usually null and the file is appended via
+  multipart form data maps.
+  """
+  file: WebformSubmissionFileUpload
+}