Fix for projects using TS-option "noUncheckedIndexedAccess"

[SimonSimCity]

When installing this plugin in a project which has the TS-option noUncheckedIndexedAccess enabled, it will fail. This PR fixes this.

It also updates some packages (all in compliance with the existing package.json definition) to allow me to run eslint.

When an icon is not found, an error is thrown instead of simply writing it out on the console. This is more in line with vue's error handling.