Add trac browser link & WordPress.org to the theme trac ticket

[grapplerulrich]

By adding the trac browser the reviewer could easily view the code in the browser with code styling and line number.

The change would be needed in WPORG_Themes_Upload ::prepare_trac_ticket()

The following code would need to be added with the SVN and ZIP links.

Trac Browser - https://themes.trac.wordpress.org/browser/{$this->theme_slug}/{$this->theme->display( 'Version' )}

[coffee2code]

In 4891:

Theme Directory: Add themes.trac browser link for the submitted version of the theme to the trac ticket.

Props grapplerulrich, SergeyBiryukov.
Fixes #2354.