FT Tutorial

[qdrn]

Make tutorial on how to create a FT.

You can base your work on the structure designed in this PR: #114
Another possible inspiration: https://docs.near.org/develop/relevant-contracts/ft. You should be able to find plenty of good tutorials on internet for inspiration.

Keep it simple and concise at first.

[qdrn]

Can you handle that @windushka when you have some spare time from your other tasks ?

[windushka]

On hold as per Grégory's request.