Keep old deprecated constant.

- Keep in case anyone was using it. Will remove later.

Author: davidlehn

CHANGELOG.md

@@ -15,6 +15,9 @@
 
 ### Changed
 - Keep term definitions mapping to null so they may be protected.
+- **NOTE**: `LINK_HEADER_REL` in `lib/constants.js` has been deprecated and
+  renamed to `LINK_HEADER_CONTEXT`. It remains for now but will be removed in a
+  future release.
 
 ## 2.0.2 - 2020-01-17
 

lib/constants.js

@@ -7,6 +7,9 @@ const RDF = 'http://www.w3.org/1999/02/22-rdf-syntax-ns#';
 const XSD = 'http://www.w3.org/2001/XMLSchema#';
 
 module.exports = {
+  // TODO: Deprecated and will be removed later. Use LINK_HEADER_CONTEXT.
+  LINK_HEADER_REL: 'http://www.w3.org/ns/json-ld#context',
+
   LINK_HEADER_CONTEXT: 'http://www.w3.org/ns/json-ld#context',
 
   RDF,