Move some classes to a new subpackage and adress requested changes

Rename URLHandler and KoreUtil classes to InternalUrlsHandler and KoreUtils.
Move InternalUrlsHandler, KoreUtils, TextLinkfier, ShareUtils classes to external_communication subpackage.
Remove unused param showPreviewText in shareText method of ShareUtils class.
Add initial work to be able to display an image preview of the content shared (not for downloads).
Use a better regular expression to parse timestamps in plain text descriptions.

app/src/main/java/org/schabi/newpipe/about/AboutActivity.kt

@@ -16,8 +16,8 @@ import org.schabi.newpipe.BuildConfig
 import org.schabi.newpipe.R
 import org.schabi.newpipe.databinding.ActivityAboutBinding
 import org.schabi.newpipe.databinding.FragmentAboutBinding
+import org.schabi.newpipe.util.external_communication.ShareUtils
 import org.schabi.newpipe.util.Localization
-import org.schabi.newpipe.util.ShareUtils
 import org.schabi.newpipe.util.ThemeHelper
 
 class AboutActivity : AppCompatActivity() {