Support linkable attribute tokens

[mportiz08]

Bug/issue #, if applicable: 108472125

Summary

This adds support for rendering certain attribute tokens as links to symbols instead of just plaintext.

As a basic example, DocC would generate a linkable @StringBuilder token in the contrived buildABC function here:

@resultBuilder
public struct StringBuilder {
  static func buildBlock(_ parts: String...) -> String {
    parts.joined(separator: "\n")
  }
}

@StringBuilder public func buildABC() -> String {
  "a"
  "b"
  "c"
}

Dependencies

swiftlang/swift#63637

Testing

To test this using swift-docc-plugin, you may need a recent 5.9 toolchain version of Swift to ensure that the symbol graph tokens get generated with the data for linking (see above dependency).

Steps:

1. Build this branch with npm run build
2. Preview docs for an example package that has an example like the one above with env DOCC_HTML_DIR=/path/to/dist swift package --disable-sandbox preview-documentation --target [target]
3. Verify that the example attribute can be clicked in a declaration, which should take you to that symbol page.

Here is an example package (target "AttributeExamples") that has the @StringBuilder example code from above:
AttributeExamples.zip

Checklist

Make sure you check off the following items. If they cannot be completed, provide a reason.

• Added tests
• Ran npm test, and it succeeded
• Updated documentation if necessary

[dobromir-hristov]

Changes look good to be, havent tested yet with docc branch.

[hqhhuang]

Looks good!

[mportiz08]

@swift-ci test