Make links to annotation documents open in new tab/window

Open links to documents in a new tab. This is important in the Notebook
view at present to "escape" the Notebook's frame, but makes sense in
all contexts as it more closely adheres to our pattern of opening links
to external properties in new windows.

src/sidebar/components/Annotation/AnnotationDocumentInfo.js

@@ -20,7 +20,13 @@ export default function AnnotationDocumentInfo({ domain, link, title }) {
     <div className="u-layout-row u-horizontal-rhythm">
       <div className="u-color-text--muted">
         on &quot;
-        {link ? <a href={link}>{title}</a> : <span>{title}</span>}
+        {link ? (
+          <a href={link} target="_blank" rel="noopener noreferrer">
+            {title}
+          </a>
+        ) : (
+          <span>{title}</span>
+        )}
         &quot;
       </div>
       {domain && <span className="u-color-text--muted">({domain})</span>}

src/sidebar/components/Annotation/test/AnnotationDocumentInfo-test.js

@@ -22,17 +22,22 @@ describe('AnnotationDocumentInfo', () => {
     assert.include(wrapper.text(), '"Turtles"');
   });
 
-  it('should render a link if available', () => {
+  it('links to document in new tab/window when link available', () => {
     const wrapper = createAnnotationDocumentInfo();
     const link = wrapper.find('a');
 
     assert.equal(link.prop('href'), 'http://www.baz');
+    assert.equal(link.prop('target'), '_blank');
   });
 
+  it('does not link to document when no link available', () => {});
+
   it('should render domain if available', () => {
-    const wrapper = createAnnotationDocumentInfo();
+    const wrapper = createAnnotationDocumentInfo({ link: '' });
 
-    assert.include(wrapper.text(), '(www.foo.bar)');
+    const link = wrapper.find('a');
+    assert.include(wrapper.text(), '"Turtles"');
+    assert.isFalse(link.exists());
   });
 
   it(