feat(card): Make `date` optional on `<ResourceCard />`

[EnMod]

🎟️ Asana Task for request prompting the change 🔢 PR on www implementing the canary release 🔍 Preview Link 🔍 Preview Link for example usage on www (see each case study library item's card)

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Description

This PR updates our <ResourceCard /> component to make showing the date optional; if no date is passed in, no date (or | separator) is shown.

PR Checklist 🚀

Items in this checklist may not may not apply to your PR, but please consider each item carefully.

• [x] Add Asana and Preview links above.
• [x] Conduct thorough self-review.
• [x] Add or update tests as appropriate.
• [x] Conduct reasonable cross browser testing for both compatibility and responsive behavior (We have a Sauce Labs account for this, if you don't have access, just ask!).
• [x] Conduct reasonable accessibility review (use the WAS as a guide or an axe browser plugin until we establish more formal checks).
• [x] Identify (in the description above) and document (add Asana tasks on this board) any technical debt that you're aware of, but are not addressing as part of this PR.

[changeset-bot[bot]]

🦋 Changeset detected

Latest commit: dd8b04a63f301a9cdb2a78a4f0c001e0ae784eeb

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

This PR includes changesets to release 2 packages

| Name | Type | | -------------------------------- | ----- | | @hashicorp/react-card | Minor | | @hashicorp/react-related-content | Patch |

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Name	Status	Preview	Comments	Updated (UTC)
react-components	✅ Ready (Inspect)	Visit Preview	💬 Add feedback	Sep 26, 2023 6:39pm

[github-actions[bot]]

:package: Canary Packages Published

Latest commit: dd8b04a63f301a9cdb2a78a4f0c001e0ae784eeb

Published 2 packages

#### @hashicorp/react-card@0.15.0-canary-20230926184001 ``` npm install @hashicorp/react-card@canary ``` #### @hashicorp/react-related-content@0.3.8-canary-20230926184001 ``` npm install @hashicorp/react-related-content@canary ```