Fix monorepo "unmet peer dependency" warnings

[edmorley]

The monorepo devDependencies equivalent of #751.

Currently after cloning the monorepo and running yarn, there are the following warnings:

warning "workspace-aggregator-550355ec-473a-4e1c-ab97-6ae35eb9323b > @neutrinojs/babel-minify > @neutrinojs/babel-minify-webpack-plugin@0.2.0" has unmet peer dependency "webpack@^2.0.0 || ^3.0.0".
warning "workspace-aggregator-550355ec-473a-4e1c-ab97-6ae35eb9323b > @neutrinojs/eslint > eslint-loader@2.0.0" has unmet peer dependency "webpack@>=2.0.0 <5.0.0".
warning "workspace-aggregator-550355ec-473a-4e1c-ab97-6ae35eb9323b > @neutrinojs/font-loader > file-loader@1.1.11" has unmet peer dependency "webpack@^2.0.0 || ^3.0.0 || ^4.0.0".
warning "workspace-aggregator-550355ec-473a-4e1c-ab97-6ae35eb9323b > @neutrinojs/font-loader > url-loader@1.0.1" has unmet peer dependency "webpack@^3.0.0 || ^4.0.0".
warning "workspace-aggregator-550355ec-473a-4e1c-ab97-6ae35eb9323b > @neutrinojs/html-template > html-webpack-template@6.1.0" has incorrect peer dependency "html-webpack-plugin@2.x".
warning "workspace-aggregator-550355ec-473a-4e1c-ab97-6ae35eb9323b > @neutrinojs/image-minify > imagemin-webpack@1.1.2" has unmet peer dependency "webpack@^2.0.0 || ^3.0.0".
warning "workspace-aggregator-550355ec-473a-4e1c-ab97-6ae35eb9323b > @neutrinojs/style-loader > extract-text-webpack-plugin@3.0.2" has unmet peer dependency "webpack@^3.1.0".
warning "workspace-aggregator-550355ec-473a-4e1c-ab97-6ae35eb9323b > @neutrinojs/font-loader > file-loader > schema-utils@0.4.5" has unmet peer dependency "webpack@^2.0.0 || ^3.0.0 || ^4.0.0".
warning "workspace-aggregator-550355ec-473a-4e1c-ab97-6ae35eb9323b > @neutrinojs/react > react-hot-loader > redbox-react@1.5.0" has unmet peer dependency "react@^0.14.0 || ^15.0.0 || ^16.0.0-beta || ^16.0.0".
warning "workspace-aggregator-550355ec-473a-4e1c-ab97-6ae35eb9323b > @neutrinojs/react > react-hot-loader > redbox-react@1.5.0" has unmet peer dependency "react-dom@^0.14.0 || ^15.0.0 || ^16.0.0-beta || ^16.0.0".

(there are actually two more, but #758 is taking care of them)

We can avoid these by adding react/react-dom/webpack to devDependencies where required.