Update documentation.

- Update supported Node.js version in README.
- Add notes about document being cloned.
- Add docs for `addStatic`.
- Update changelog with more details about cloning and potential need
  for a polyfill.

CHANGELOG.md

@@ -1,10 +1,15 @@
 # jsonld-document-loader
 
-## 2.0.1 -
+## 2.1.0 - 2024-xx-xx
 
 ### Changed
-- `addStatic` deep clones documents to avoid mutation.
-  - Use of [structuredClone](https://developer.mozilla.org/en-US/docs/Web/API/structuredClone) might require polyfill.
+- `addStatic` deep clones documents to avoid shared document mutation issues.
+  - The clone adds potential time and memory use considerations depending on
+    the frequency of `addStatic` calls and on document size. For expected use
+    cases this should be minimal.
+  - [structuredClone](https://developer.mozilla.org/en-US/docs/Web/API/structuredClone)
+    is used and may not be available in old browsers and Node.js before v17.
+    Use a polyfill if needed.
 
 ## 2.0.0 - 2023-02-06
 

README.md

@@ -25,7 +25,7 @@ TBD
 
 ## Install
 
-- Node.js >= 16 is required.
+- Node.js >= 18 is required.
 
 ### NPM
 
@@ -57,7 +57,7 @@ const loader = new JsonLdDocumentLoader();
 
 The `addStatic()` method allows developers to load fixed static contexts and
 documents, to ensure known versions and contents, without going out to the
-network.
+network. The context is cloned when added.
 
 For example, to add support for the DID Core context, the VC context, and crypto
 suite specific contexts:

lib/JsonLdDocumentLoader.js

@@ -8,6 +8,15 @@ export class JsonLdDocumentLoader {
     this.protocolHandlers = new Map();
   }
 
+  /**
+   * Adds a URL to document mapping to the loader.
+   *
+   * The document will be cloned.
+   *
+   * @param {string} url - The URL of a document,
+   *   etc.
+   * @param {object} document -The document.
+   */
   addStatic(url, document) {
     if(!_isString(url)) {
       throw new TypeError('The first parameter (url) must be a string.');