My go at a procedural implementation example of subscriber node

[ru2saig]

Refer to https://github.com/fmrico/book_ros2/issues/25

[fmrico]

Hi,

Tests are failing, as you can see at log, because:

• There are extra spaces at the end of line 4
• In line 9, you need a space to both sides of '*'
• You need to add the copyright with your name in this file

[ru2saig]

Ah I see, thanks. I believe I've fixed them now!

[fmrico]

Thanks!!!

merging :rocket: