Use node ecosystem for managing dependencies and bundling assets

[mscottford]

The Freshli.Web project was generated by running dotnet new mvc. The way that template handles browser-based assets is not ideal for these reasons:

• Dependencies are copied directly into the repository and are not tracked by a dependency manager
• The bundling support built into ASP.NET Core is limited to minification. More advanced support such as shims and transpiling from one JS syntax to another are not supported

So instead, let's switch to using tools from the node ecosystem to solve this problem. We'll start with using yarn for dependencies and perhaps use webpack for bundling and other features.