Use chars instead of values for OpenAnnotation

__tests__/src/lib/AnnotationResource.test.js

@@ -26,14 +26,14 @@ describe('AnnotationResource', () => {
   describe('tags', () => {
     it('when only motivation', () => {
       expect(
-        new AnnotationResource({ resource: [{ '@type': 'oa:Tag', value: 'yo' }, { '@type': 'oa:Tag', value: 'lo' }] }).tags,
+        new AnnotationResource({ resource: [{ '@type': 'oa:Tag', chars: 'yo' }, { '@type': 'oa:Tag', chars: 'lo' }] }).tags,
       ).toEqual(['yo', 'lo']);
     });
     it('when multiple motivations', () => {
       expect(
         new AnnotationResource({
           motivation: ['oa:commenting', 'oa:tagging'],
-          resource: [{ '@type': 'oa:commenting', value: 'yo' }, { '@type': 'oa:Tag', value: 'lo' }],
+          resource: [{ '@type': 'oa:commenting', chars: 'yo' }, { '@type': 'oa:Tag', chars: 'lo' }],
         }).tags,
       ).toEqual(['lo']);
     });

src/lib/AnnotationResource.js

@@ -53,9 +53,9 @@ export default class AnnotationResource {
   /** */
   get tags() {
     if (this.isOnlyTag()) {
-      return this.resources.map(r => r.value);
+      return this.resources.map(r => r.chars);
     }
-    return this.resources.filter(r => r['@type'] === 'oa:Tag').map(r => r.value);
+    return this.resources.filter(r => r['@type'] === 'oa:Tag').map(r => r.chars);
   }
 
   /** */