feat: add pageSize option

[angeloashmore]

Package

• gatsby-source-prismic
• gatsby-plugin-prismic-previews

Types of changes

• Chore (a non-breaking change which is related to package maintenance)
• Bug fix (a non-breaking change which fixes an issue)
• New feature (a non-breaking change which adds functionality)
• Breaking change (fix or feature that would cause existing functionality to change)

Description

Adds a pageSize plugin option to gatsby-source-prismic and gatsby-plugin-prismic-previews which allows setting the pageSize option to @prismicio/client.

This allows a user to reduce API payloads during node sourcing by setting the page size to less than the maximum (100). This may be necessary if the Prismic REST API fails the request due to result that is larger than the maximum payload size.

Checklist:

• My change requires an update to the official documentation.
• All TSDoc comments are up-to-date and new ones have been added where necessary.
• All new and existing tests are passing.