[PVC] Consider setting a max-width on breadcrumbs to help with long breadcrumb items

[joshblack]

Context from Slack: https://github.slack.com/archives/CSGAVNZ19/p1727849002947669

In certain situations, a breadcrumb item may be long like on this page: https://github.com/actions/setup-node/pkgs/container/setup-node/276316120?tag=sha256-c6641e273d9f0bb6098ec9bc014e17251310b74fe49f2e082364cdcb044a7814

In these scenarios, the breadcrumbs component will overflow the page. Based on the conversation in Slack, it'd be great if we could set a max-width (or something similar) on the item so that this does not occur.

[lesliecdubs]

Notes from Primer triage: we can just apply a max-width, no concerns about losing content that gets cut off. Suggestion from the Slack thread:

We could fix this by adding max-width: 100%; to the breadcrumb-item.

[lesliecdubs]

This came up in Primer Brand as a potential accessibility issue: https://github.com/github/primer/issues/3755.

We'll add this to the PVC accessibility remediation batch (via addition to that work's project board https://github.com/orgs/github/projects/13460/views/4) to be looked into.