Feat: On Modal open, show items found for Highlighted text

[badasswp]

This PR resolves this issue.

Description / Background Context

At the moment, when a user selects a text and opens up the search and replace modal, we don't see the number of items that are found immediately. This PR resolves this issue so that when users select a text in the block editor and open up the modal, they are immediately shown the number of items found, if any.

Testing Instructions

• Pull PR to local.
• Build correctly using yarn build.
• Highlight any text in the block editor.
• Click on Search & Replace icon.
• Observe that number of items found are shown immediately in the modal.
• Close Modal.
• Deselect highlighted text and open modal again.
• Observe that number of items are not shown since no text is highlighted.
• Observe that there are no regressions introduced as a result of this change.