Fixed setup for examples in readme

[peterkogo]

For running the examples it is not enough to install rollup globally. The dependencies should be installed instead.

Instead of

npm i --global rollup

you should

npm install

[Horusiath]

Thanks @peterkogo . Have you actually checked if it's safe to remove npm i --global rollup for people who haven't got it already installed?

[peterkogo]

@Horusiath Yes, it's inside the package dependencies anyways so it will be installed with npm install.