Gwen Stefani has helped husband Blake Shelton celebrate an incredible professional achievement, as the country star enjoys 20 years in the industryTaking to social media, Gwen shared a snap that saw the pair holding up a very large plaque from Recording Industry Association of America (RIAA) that celebrated 13 million RIAA Album Awards, and 52 million RIAA Singles.The plaque also featured covers of his albums, singles and EPs from his career and Gwen captioned the post: "Congratulations to this