EOL add mixed detection

[zekth]

Add mixed detection
deleted double entry for io/test

Like mentionned in : #289

[ry]

I'd rather if we did the move separately. My idea is that we could also move

//toml/toml.ts -> //encoding/toml.ts
//fs/eol.ts -> //encoding/eol.ts
//bytes/bytes.ts -> //encoding/bytes.ts

I'm not sure if "encoding" is a good name tho. Basically I'd like to combine all the "file formats" into one place. Maybe @keroxp has a better suggestion for organization?

[ry]

For this PR please undo the moves, but leave the other changes. Update the commit message.

[ry]

LGTM