Celtic have yet to make their first signing of the summer transfer window but the club continue to be linked to a variety of talents around the world. The goalkeeping position is the top priority after the retirement of Joe Hart with Peter Vindahl Jensen and Martin Dubravka the most reported on options from a list of 20 in total. However, other areas of the pitch could do with strengthening too. A left-back is undoubtedly needed alongside other defensive options, midfielders and attackers. Over the weekend, it emerged that one forward Celtic are showing interest in is Costa Rica international …