Chapter about dicts

[alexmojaki]

Part of #165

I've written a partial draft of a chapter about dictionaries here: https://demo.hedgedoc.org/OH78A7uwTDOjeMM4v0QFLg?edit

It's not complete, but a lot has been written, and the actual implementation of the existing content can start now, although suggestions for changes are still welcome.

[AndrewPluzhnikov]

Alex,
I've read the draft and I have a few suggestions.

• In the nested language dictionaries example, you use f-strings. I think we can avoid using these here - I don't think they are needed.
• Could we use quantity and quantities instead of amount and amounts? Amounts are generally used for uncountable values, while quantities can be used for both countable and uncountable values.

I will go ahead and start implementing the draft.

[alexmojaki]

This chapter is going to be added after all the other existing chapters, i.e. after the tic-tac-toe project. f-strings have been introduced and used several times, and I think it's best to keep using them.

Changing amount to quantity sounds fine.

Thanks for implementing!

[alexmojaki]

Next work on this is in #370 (comment)