I actually had the same question before I applied but for JLPT (the Japanese equivalent of HSK). If Corona hadn't happened and I was actually able to take the exam I may well have included it in my application. However, it's obviously not something admissions tutors would consider to be a deal breaker (unless your course is specifically relevant to Chinese). Particularly in the UK where we have a limited amount of characters to include in our personal statement, it would be better advised to include skills more closely associated with your applied course. Unless you're struggling on things to include I wouldn't advise devoting too many lines to your Chinese skills (although is is very impressive!).