feat: add Node.getIf method

[RavenColEvol]

Description
This PR is an attempt to solve below issue and provide a graceful method to get a Node.

Issue
Fixes: #4845

Example

// If node exists
const node = Node.getIf(editor, [0]); // returns respective node

// If node doesn't exist
const node = Node.getIf(editor, [0]); // return undefined rather than error

Context
I simply used the existing logic of get method and instead of throwing any error returned undefined

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.)

[changeset-bot]

🦋 Changeset detected

Latest commit: 85452bf

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

This PR includes changesets to release 1 package

Name	Type
slate	Patch

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