fix: add date_published selector in www.sanwa.co.jp extractor (#378)

Author: kik0220

src/extractors/custom/www.sanwa.co.jp/index.js

@@ -7,7 +7,11 @@ export const WwwSanwaCoJpExtractor = {
 
   author: null,
 
-  date_published: null,
+  date_published: {
+    selectors: ['p.date'],
+    format: 'YYYY.MM.DD',
+    timezone: 'Asia/Tokyo',
+  },
 
   dek: {
     selectors: [['meta[name="og:description"]', 'value']],

src/extractors/custom/www.sanwa.co.jp/index.test.js

@@ -58,7 +58,7 @@ describe('WwwSanwaCoJpExtractor', () => {
 
       // Update these values with the expected values from
       // the article.
-      assert.equal(date_published, null);
+      assert.equal(date_published, '2019-03-07T15:00:00.000Z');
     });
 
     it('returns the dek', async () => {