Improve header in README.md based on name and description

[gsmet]

And also allows to not include the default content with a particular extension.

@ia3andy I did two changes here:

• now that we have the name and the description of the project, we can use them in the README.md
• I also included a boolean to be able to disable the default content. I agree that it's only to be used in very specific cases but I don't think it hurts as it's pretty straightforward

I think that there are extensions that really redefines what the project is about such as my Quarkus GitHub Action thing, but also lambdas where we will probably want a completely different content in the README.

Maybe we could think about allowing that more cleanly but in the meantime having this simple hack would help (in my case, I don't expect any additional extensions providing content to the README so it works pretty much OK).

If you really feel strongly about the second change, I can go back to just the first one.

Keeping as draft until I have your opinion.

[ia3andy]

That seems like a smart move 👍

[ia3andy]

Just we need to make sure no extension codestart is setting it to true :) (it would behave inconsistently and randomly)

[gsmet]

Yeah, I would lean towards keeping it a hidden 'feature' and not invest much more time on it except if we have complaints.

[gsmet]

@ia3andy this is now ready for review!

[ia3andy]

Cool!

[quarkus-bot]

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