Fix example

[fdietze]

fixes #58

There were two issues here:

1. npm 7.6.3 was not able to resolve the dependencies (I don't know why)

[info] Fast optimizing /tmp/tmp.4XopoXrhQQ/apollo-scalajs/example/target/scala-2.12/scalajs-bundler/main/react-apollo-scalajs-example-fastopt.js
[error] npm ERR! code ERESOLVE
[error] npm ERR! ERESOLVE unable to resolve dependency tree
[error] npm ERR! 
[error] npm ERR! While resolving: undefined@undefined
[error] npm ERR! Found: webpack@4.32.2
[error] npm ERR! node_modules/webpack
[error] npm ERR!   dev webpack@"4.32.2" from the root project
[error] npm ERR! 
[error] npm ERR! Could not resolve dependency:
[error] npm ERR! peer webpack@"^2.0.0 || ^3.0.0" from file-loader@1.1.5
[error] npm ERR! node_modules/file-loader
[error] npm ERR!   dev file-loader@"1.1.5" from the root project
[error] npm ERR! 
[error] npm ERR! Fix the upstream dependency conflict, or retry
[error] npm ERR! this command with --force, or --legacy-peer-deps
[error] npm ERR! to accept an incorrect (and potentially broken) dependency resolution.

2. Since apollo-cli is added as a devDependency, but the command executed the globally installed version, there was a confusion with the versions. Using npx should ensure that the apollo installed inside the project is used.

[apollo-cla]

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