Add meaningful code examples to Storybook

[joao-m-santos]

Feature description

Add source code examples to the Storybook Stories.

Problem/motivation

It is sometimes difficult to understand Lume component usage for devs new to the library. Thus, having "copy-pastable" examples of the Stories would be very useful.

Describe alternatives you've considered

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Additional context

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Validations

• [X] Follow our Code of Conduct
• [X] Read the Contributing Guidelines.
• [X] Check that there isn't already an issue that request the same feature to avoid creating a duplicate.