Installation script should check for ESLint dependencies presence

[IlCallo]

Currently the installation script take as assumptiom that ESLint dependencies are already installed by the core, but I guess this is not always the case.
At the very least we should use hasPackage to check for all packages needed by the extension, but that could already be there from the initial project creation.

This could be due to the fact that ESLint is not mandatory, but added when the project is created.
It must also be decided where these dependencies should be put, as per #22 (comment)

Should them be put into AE dependencies? Or as peerDependencies? Or added to the user project package.json?

[IlCallo]

Should be fixed by #48