Deprecating webpack@2&3, html-webpack-plugin@2&3, Bumping deps

• #64, #65, #66, #67 bumped dependencies from dependabot
• #69 added webpack@5 as a peer dependency, thanks to @david-fong
• #71 upgraded all deps in package.json to their latest versions
• Deprecation: #72 deprecated webpack 2 and 3, and html-webpack-plugin 2 and 3, and set webpack@5 as the new package to test changes against