bump eslint peerDep to eslint@6

[amilajack]

No description provided.

[ljharb]

Make sure it’s added to CI too - if it’s not tested it’s not supported.

[amilajack]

Tests are passing with eslint@6 but linting doesn't pass because of the following error:

Error: Failed to load plugin 'import' declared in 'package.json » eslint-config-bliss » eslint-config-ai
rbnb-base » /.../node_modules/eslint-config-airbnb-base/
rules/imports.js': Cannot find module 'eslint/lib/util/source-code'
Require stack:

[ljharb]

That might need to wait on the next version of the import plugin being published.

[tbroyer]

eslint-plugin-import 2.18.0 has been released: https://github.com/benmosher/eslint-plugin-import/blob/master/CHANGELOG.md