docs(core): example in readme

Proposed Changes

Bugfix in readme

Seems the context doesn't have name attribute

ERROR:    [alice]: Exception in interval handler: 'InternalContext' object has no attribute 'name'
Traceback (most recent call last):
  File "/Users/tomasz.strzeszkowski/.pyenv/versions/3.11.2/lib/python3.11/site-packages/uagents/agent.py", line 73, in _run_interval
    await func(ctx)
  File "<stdin>", line 3, in say_hello
AttributeError: 'InternalContext' object has no attribute 'name'

Issues

https://github.com/fetchai/uAgents/issues/395

Types of changes

What types of changes does the pull request introduce? Put an x in the boxes that apply:

[x] Bug fix (non-breaking change that fixes an issue).
[ ] New feature added (non-breaking change that adds functionality).
[ ] Breaking change (fix or feature that would cause existing functionality to stop working as expected).
[x] Documentation update.
[ ] Something else (e.g., tests, scripts, example, deployment, infrastructure).

Checklist

Put an x in the boxes that apply:

[x] I have read the CONTRIBUTING ↗️ guide.
[x] Checks and tests pass locally.

If applicable

[ ] I have added tests that prove my fix is effective or that my feature works.
[ ] I have checked that code coverage does not decrease.
[x] I have added/updated the documentation.

Further comments

(If this is a relatively large or complex change, kick off a discussion by explaining why you chose the solution you did, what alternatives you considered, etc...).

fetchai / uAgents

docs(core): example in readme #396