examples: add an example script for sending ussd codes

[mmubarak0]

I do not know how, but sending a USSD code improves internet speed. It sometimes fixes the connection, which makes me send USSD codes frequently. other people may want to use it differently. maybe for knowing the data status more accurately than the one the UI shows. I have added some colors and waiting animation to make it visually appealing.
I'm not an experienced developer so any feedback would be helpful thanks.

[Salamek]

Anyway, code could be bit better and simpler (single thread), but it is ~ok as an example i guess so please just fix that one bug and i'll merge ;-)

[Salamek]

Ok, also there are some lint issues:

examples/send_ussd.py:38: error: Function is missing a return type annotation  [no-untyped-def]
  examples/send_ussd.py:38: note: Use "-> None" if function does not return a value
  examples/send_ussd.py:60: error: Non-overlapping equality check (left operand type: "Dict[str, Any]", right operand type: "Literal['OK']")  [comparison-overlap]
  Found 2 errors in 1 file (checked 108 source files)

[mmubarak0]

I did fix these errors now but I think I have done it the wrong way by running mypy . manually.
what is the recommended way for running the lints checks?

[Salamek]

Running mypy . locally should do the trick, try to push those changes here and see how it goes ;-)