More robust Rich Text and Title mock values

[angeloashmore]

Is your feature request related to a problem? Please describe.

Creating Rich Text and Title mock values is currently limited. It generates values for most block types, such as headings and images, but does not include some like links.

Rich Text and Title mock values can be customized using "pattern" option. Depending on the selected pattern, such as "short" and "long", the length of the value can be loosely determined. This gives some control of the output, but does not allow for custom patterns.

Describe the solution you'd like

To give more control over the created mock value, access to individual block value generators can be provided by the library. This allows users to create custom values like:

• Heading 1
• Paragraph
• Paragraph

This can be useful when you have a general idea of the type of content that will be provided by editors.

This requires all block types to be supported, including links.

Someone could use the individual value generators like this:

import * as prismicT from '@prismicio/types'
import * as prismicM from '@prismicio/mock'

const richTextValue: prismicT.RichTextField = [
  prismicM.value.richTextBlocks.heading1({ pattern: 'medium' }),
  prismicM.value.richTextBlocks.paragraph(),
  prismicM.value.richTextBlocks.paragraph(),
]

Describe alternatives you've considered

Mock values can be constructed by hand. Some guidance is provided thanks to @prismicio/types. Manually creating mock values is not ideal for obvious reasons.

Additional context

N/A