[Feature Request] Allow Tour Readers to ask questions and read past answered ones

[felipetesc]

Hello. I don't know if that's an interesting request, but I'll suggest anyway. My request can allow to docs to be continually enhanced when we are reading it.
While diving into the Language Tour, I started to have some doubts about some points related to the language, and I though it could prove helpful if we could make questions by asking them at the moment of our reading. However, it would be needed to have some type of authentication. Also, it can help new readers to read previously asked question, don't leave the tour , and finished it with joy.
Thanks !