Add link to examples and revealjs.com to index.html slide

[timabell]

Took me a little while to find the examples, so this makes them a bit more discoverable.

Thanks for software, very useful.

Before

After

[t-fritsch]

thanks for the PR @timabell ! 🙏

Making examples more visible is a good idea, maybe adding this to the README would be better (in the list of links in getting started section) ?

I guess @hakimel leaves default slides empty (apart "Slide 1" and "Slide 2" titles) to keep the default deck really simple, but maybe having this in the first slide is fine tho ?

Regarding the examples/index.html and examples/build-index.sh I wonder if it is really needed since we already have a file listing in the defaut webserver (launched with npm start) :