fix: add documentation for many classes where it was missing

src/ldp/representation/NamedRepresentation.ts

@@ -1,6 +1,9 @@
 import { Representation } from './Representation';
 import { ResourceIdentifier } from './ResourceIdentifier';
 
+/**
+ * A {@link Representation} with an identifier.
+ */
 export interface NamedRepresentation extends Representation {
   /**
    * The identifier of this representation.

src/ldp/representation/RepresentationMetadata.ts

@@ -3,6 +3,9 @@
  */
 import { Quad } from 'rdf-js';
 
+/**
+ * Metadata corresponding to a {@link Representation}.
+ */
 export interface RepresentationMetadata {
   /**
    * All metadata triples of the resource.