Add Created and modified Dublin code attributes

lib/domain/dublin_core/dublin_core.dart

@@ -9,6 +9,8 @@ class DublinCore {
   final String publisher;
   final String contributor;
   final String date;
+  final String created;
+  final String modified;
   final String type;
   final String format;
   final String identifier;
@@ -26,6 +28,8 @@ class DublinCore {
     this.publisher,
     this.contributor,
     this.date,
+    this.created,
+    this.modified,
     this.type,
     this.format,
     this.identifier,
@@ -48,6 +52,8 @@ class DublinCore {
       publisher: findElementOrNull(element, "dc:publisher")?.text,
       contributor: findElementOrNull(element, "dc:contributor")?.text,
       date: findElementOrNull(element, "dc:date")?.text,
+      created: findElementOrNull(element, "dc:created")?.text,
+      modified: findElementOrNull(element, "dc:modified")?.text,
       type: findElementOrNull(element, "dc:type")?.text,
       format: findElementOrNull(element, "dc:format")?.text,
       identifier: findElementOrNull(element, "dc:identifier")?.text,

test/rss_test.dart

@@ -240,6 +240,8 @@ void main() {
     expect(feed.dc.publisher, "publisher");
     expect(feed.dc.contributor, "contributor");
     expect(feed.dc.date, "2000-01-01T12:00+00:00");
+    expect(feed.dc.created, "2000-01-01T12:00+00:00");
+    expect(feed.dc.modified, "2000-01-01T12:00+00:00");
     expect(feed.dc.type, "type");
     expect(feed.dc.format, "format");
     expect(feed.dc.identifier, "identifier");

test/xml/RSS-DC.xml

@@ -25,6 +25,8 @@
             <dc:publisher>publisher</dc:publisher>
             <dc:contributor>contributor</dc:contributor>
             <dc:date>2000-01-01T12:00+00:00</dc:date>
+            <dc:created>2000-01-01T12:00+00:00</dc:created>
+            <dc:modified>2000-01-01T12:00+00:00</dc:modified>
             <dc:type>type</dc:type>
             <dc:format>format</dc:format>
             <dc:identifier>identifier</dc:identifier>