Fix escapejs return type

This commit changes `escapejs` filter to return binary, when it received binary as input.

Couple of weeks ago I proposed to use `unicode:characters_to_list` in `escapejs` to fix a bug
with handling 'line separator' and 'paragraph separator'.

Even, when it got binary as input, `escapejs` returned list as output,
so I left it that way, but I believe, it should return binary, when it receives binary.
For example `first` filter works this way.