Your task is to create a program or a function that, given an input, outputs the input text with random letters capitalized, while keeping already capitalized letters capitalized.
Every combination of capitalizations of the lowercase letters should be possible. For example, if the input was
abc, there should be a non-zero probability of outputting any of the following combinations:
Your input is a string, containing any number of printable ASCII characters, for example
Hello World. The outputs for that input include
HElLO WOrld, etc.
This is code-golf, so the shortest answer in each language wins!