Release 5.2.1

• update CHANGELOG (6440486)
• Keep replacement cache values when an older promise settles (#164) (2dc62a7)
• Bump source-map-js (#163) (c5ac7c2)
• Bump the npm_and_yarn group across 1 directory with 2 updates (#162) (4841400)
• Bump serialize-javascript (#161) (1639d3e)
• docs: correct option, cache and statistics examples (#160) (c6e6374)