[Draft] Avoid TextString unmounting when rendering zero-width strings and line breaks

[clauderic]

Description
This is a draft PR to refactor how zero-width strings and line breaks are rendered in the leaf <String /> component. Currently, we conditionally render either the <TextString> component, or the <ZeroWidthString> component, which both ultimately render <span> elements to the DOM.

When we switch from rendering a <TextString> component to a <ZeroWidthString> component, React needs to first unmount the <TextString> component, which removes the text <span> from the DOM, and insert a new span when the <ZeroWidthString> component mounts.

This is wasteful from a performance point of view, and can also interrupt composition events on Android.

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]

⚠️ No Changeset found

Latest commit: efb58f3

Merging this PR will not cause a version bump for any packages. If these changes should not result in a new version, you're good to go. If these changes should result in a version bump, you need to add a changeset.

This PR includes no changesets

When changesets are added to this PR, you'll see the packages that this PR includes changesets for and the associated semver types

Click here to learn what changesets are, and how to add one.

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