feat(core): Create types and utilities for span links

Author: s1gr1d

packages/core/src/types-hoist/index.ts

@@ -113,6 +113,7 @@ export type {
   SpanContextData,
   TraceFlag,
 } from './span';
+export type { SpanLink, SpanLinkJSON } from './link';
 export type { SpanStatus } from './spanStatus';
 export type { TimedEvent } from './timedEvent';
 export type { StackFrame } from './stackframe';