Styled components - naming convention

[gomorizsolt]

There's no relevant issue.

For some insights, see the referenced comments:

• #1,
• #2,
• #3.

Changes:

• extended the Conventions phase with Naming,
• added practical examples for both cases,
• updated CSS-in-JS examples accordingly.

It might be unnecessary to demonstrate examples in this phase as CSS-in-JS already does it. On the other hand, IMO it's a good practice to place the examples where they belong to.

What do you think?