Add support for plain text breadcrumb elements

[pixelprodev]

Changes proposed in this PR:

• Add span elements to already existing declarations for breadcrumb styles

Reviewer, please refer to this "definition of done" checklist:

Please confirm the following before accepting this PR:

• Any acceptance criteria have been met
• Functionality has been manually tested in a testing app on desktop
• Functionality has been manually tested in a testing app on phone
• Any necessary unit, regression and integration tests have been added or updated
• All automated tests pass including accessibility
• No linting or build errors
• No high priority bugs are open
• All documentation has been updated
• Release notes have been updated

After accepting, please remind developer to merge code into all appropriate development branches.

[salesforce-ux-bot]

By analyzing the blame information on this pull request, we identified @brandonferrua, @kaelig and @aputinski to be potential reviewers

[houndci-bot]

Each selector in a comma sequence should be on its own single line

[pixelprodev]

#242

[kaelig]

This should probably be a > span to avoid propagation of styles to potential other children.

[kaelig]

A huge "thank you" for your contribution, @pixelprodotco!

Let us check first if this pattern is desirable from an accessibility / usability point of view, and we'll get back to you shortly.

[pixelprodev]

sounds good. thanks.

[kaelig]

Thanks again for our contribution, @pixelprodotco! Our design team looked into this pattern and it seems the Design System's guidelines should not include the proposed variant. In case this pops up in future design discussions I'll make sure to point to your contribution.