support Oneshot for mangadex (#581)

* support Oneshot for mangadex

src/all/mangadex/build.gradle

@@ -5,7 +5,7 @@ ext {
     appName = 'Tachiyomi: MangaDex'
     pkgNameSuffix = 'all.mangadex'
     extClass = '.MangadexFactory'
-    extVersionCode = 40
+    extVersionCode = 41
     libVersion = '1.2'
 }
 

src/all/mangadex/src/eu/kanade/tachiyomi/extension/all/mangadex/Mangadex.kt

@@ -338,6 +338,10 @@ open class Mangadex(override val lang: String, private val internalLang: String,
             }
             chapterName.add(chapterJson.get("title").string)
         }
+        //if volume, chapter and title is empty its a oneshot
+        if(chapterName.isEmpty()){
+            chapterName.add("Oneshot")
+        }
         if ((status == 2 || status == 3) && doesFinalChapterExist(finalChapterNumber, chapterJson)) {
             chapterName.add("[END]")
         }