Publish CodeChica++ lesson 0x04

[xlgmokha]

Why is this needed?

I need to publish this to the website so that my class know what they are supposed to learn today and so that I know what I'm supposed to teach them.

What does this do?

It adds a link to the new lesson page and it updates the agenda for that lesson.

Type of change

• [X] New feature (non-breaking change which adds functionality)

[AlisaSalikhov]

Who is who