Create "like" button

[amorriscode]

Each learning should have a like button.

We have an icon for "liking" a learning.

• The Learning data model allows likes
• In the Learning service we need to create a method for liking; basically a copy of the update method but we won't have to protect it
• That method should copy the existing likes and simply push a userId (the one in context) into the likes array
• You can see how to get a user from context on this line of code
• Read about doing onClick in React here: https://reactjs.org/docs/handling-events.html; we will want to do that to handle a user clicking