Improve readme readability

[alelb]

• Add titles to the examples
• Add bulleted list for the implemented features

[alelb]

@leodido take a look at Readme.

I added a feature section and the titles of the examples.

That's to be continued.

[leogr]

I suggest to make a ToC instead of a simple bullets list of features

[leodido]

I saw it.

I refined the titles and the TOC.

I think we still miss to show some capabilities of our components.

Furthermore the styling section is not complete.

Ideally we should provide also some example of chips with custom styles/colors.

Anyway I'm adding a section to show the declarative insertion of \<paper-chip\> within \<paper-chip-input\>.

Please review my commit and continue.