support other fuzzy finders

[Konfekt]

Fuzzy finders such as sk, peco and fzy offer similar functionality to that of fzf, even their command-line arguments mostly coincide with that of fzf. (For example, here are some commands that work exactly the same among all of these fuzzyfinders.) Other than -ansi and -d, which is only supported by sk, those used in fzf-tab-completion seem to be supported by all other mentioned fuzzy finders.

Regarding sk, the value of _FZF_COMPLETION_SEP=$'\x7f' is not interpreted correctly (and the recent change to $\x01 suppresses all output) , but say _FZF_COMPLETION_SEP=$'\x20' at least does not produce unknown characters.
Perhaps it is not difficult after to all to adapt it to other fuzzy finders, at least sk, which comes closest to fzf?

[lincheney]

doesn't sound like a bad idea
I don't use any of the other fuzzy finders, so I don't personally have any interest in adding support, but I won't say no to a PR if someone else does.
With the separator, it should be something that doesn't print out or the fzf UI will be messed up, so 0x20 won't work.