Update Sources/Instrumentation/Instrument.swift

Co-authored-by: Konrad `ktoso` Malawski <[email protected]>

Author: heckj

Sources/Instrumentation/Instrument.swift

@@ -36,6 +36,9 @@ public protocol Extractor: Sendable {
 /// A type that allows you to inject values to an associated carrier.
 ///
 /// The associated type, `Carrier`, is often a client or outgoing request into which values are inserted for tracing spans.
+
+/// Typically the library adopting instrumentation, would provide an implementation of this type, since it is aware of its carrier type. 
+/// Which then can be combined with instrumentation or tracing implementations, which are not aware of the concrete carrier, and only provide an ``Instrument`` (or `Tracer`) which makes use of injector/extractor to operate on carrier values.
 public protocol Injector: Sendable {
     /// The carrier to inject values into.
     associatedtype Carrier: Sendable