docs: clarify resource identity and add community blog post

[ShantKhatri]

What is the motivation?

The current documentation does not explicitly detail how resource UIDs are constructed or how identity matching works under the hood. Clarifying this process helps developers understand how to correctly use the id field and realize that "shared resources" are simply the result of identity matching rather than a separate primitive in the spec. Additionally, we want to surface a recent community blog post that dives deep into this resolution process.

What does this change do?

• Adds a new Resource identity section to resources-provisioners.md for both score-compose and score-k8s. This section clearly breaks down how a resource UID is constructed (type.class#workload_name.resource_name) and explains the behavior of the id field.
• Adds the recent blog post "Anatomy of a score.yaml: How Resolution Actually Works" to the external blog posts list in content/en/docs/community/_index.md.

What is your testing strategy?

• Verified that the markdown renders correctly.
• Confirmed that the added blog post link in the community index resolves successfully.

Is this related to any issues?

No. Adding these has been discussed with @mathieu-benoit over Slack.

Have you read the Contributing Guidelines?

• I have read the Contributing Guidelines

[mathieu-benoit]

LGTM, great clarification and addition, thanks @ShantKhatri!