Add support for JSX components in slate-hyperscript

[12joan]

Description
This PR adds support for JSX components in slate-hyperscript, analogous to React components.

Example

interface MentionProps {
  id: string
  children: unknown
}

function Mention({ id, children }: MentionProps) {
  return <element inline id={id}>{children}</element>
}

const element = (
  <element>
    This is <Mention id="alice-123">Alice</Mention>.
  </element>
)

Context
Complex applications using Slate sometimes require repetitive, deeply nested JSX for their tests. Using components lets us refactor out this JSX into reusable, logical units.

Checks

• The new code matches the existing patterns and styles.
• The tests pass with yarn test.
• The linter passes with yarn lint. (Fix errors with yarn fix.)
• The relevant examples still work. (Run examples with yarn start.)
• You've added a changeset if changing functionality. (Add one with yarn changeset add.)

[changeset-bot]

🦋 Changeset detected

Latest commit: 0a7e31e

The changes in this PR will be included in the next version bump.

This PR includes changesets to release 1 package

Name	Type
slate-hyperscript	Minor

Not sure what this means? Click here to learn what changesets are.

Click here if you're a maintainer who wants to add another changeset to this PR

[12joan]

From yarn fix