Add nested lists to formatting

Brief:

Currently, lists functionality is restricted to either ordered OR unordered:

1. Text.

OR

• Text.

Getting

1. Ordered:
   ● With unordered;
   ● And unordered;
2. Continued by ordered.

Requires some magic involved

And sometimes makes structuring info a bit difficult.

What to add:

1. Allow to mix ordered and unordered lists with proper indentation.
2. Add nested counters (by increasing indent inside list, or better by a separate button; sometimes 1.1.-1.2. work better).