fix(breadcrumb): separator is not announced by narrators

[liamdebeasi]

Pull request checklist

Please check if your PR fulfills the following requirements:

• Tests for the changes have been added (for bug fixes / features)
• Docs have been reviewed and added / updated if needed (for bug fixes / features)
  • Some docs updates need to be made in the ionic-docs repo, in a separate PR. See the contributing guide for details.
• Build (npm run build) was run locally and any changes were pushed
• Lint (npm run lint) has passed locally and any fixes were made for failures

Pull request type

Please check the type of change your PR introduces:

• Bugfix
• Feature
• Code style update (formatting, renaming)
• Refactoring (no functional changes, no api changes)
• Build related changes
• Documentation content changes
• Other (please describe):

What is the current behavior?

Issue URL: N/A

The separator for breadcrumbs could be highlighted by narrators. These separators are only visual and do not provide any additional context regarding any of the breadcrumb items.

What is the new behavior?

• All separators are now hidden from screen readers, including custom separators.

Does this introduce a breaking change?

• Yes
• No

Other information