Pass context from a parent command to its subcommand

## Note
Right now it is impossible to pass a context from one command to another:
```python
# candies/cli/parsers/parser.py

class Invocation:

    def __call__(self, command, context):
        if context is not None:
            raise NotImplementedError
        ...
```
An implementation for a case when `context is not None` should be added.