Update the "Secretly sharing files with OnionShare and TorBrowser" exercise to mention modern OnionShare features about meta

[fabacab]

@aubrel Good one for your Study Tree pick-ups?

[aubrel]

Yes it would be!

[fabacab]

I'm unsure if this is of interest to you, @notmike, but if so, have a look at the latest OnionShare and feel free to suggest any improvements to our current exercise. Thanks again for your prior contributions.

[fabacab]

I made some major edits to this exercise today and, while I didn't hit on all of these topics, much of this issue has been address by my recent editing. Closing this. Feel free to open new issues with more granular tasks if desired.