Split the package into framework-specific plugins

[sis0k0]

Follows up on #685

What?

The nativescript-dev-webpack package will be split into several packages that are framework-specific:

• @nativescript/webpack-core will contain the common build logic and will NOT be a dependency in the user projects. It will be a dependency of the framework-specific packages.
• @nativescript/webpack-ng will be the webpack build package for NativeScript Angular projects.
• @nativescript/webpack-vue will be the webpack build package for NativeScript Vue projects.
• @nativescript/webpack-ts will be the webpack build package for NativeScript TypeScript projects.
• @nativescript/webpack-js - will be the webpack build package for NativeScript JavaScript projects.

How?

Monorepo, managed with Lerna.

Migration

The nativescript-dev-webpack plugin will be deprecated and the new packages will be released. The developers should start using framework-specific plugins in their projects.
For example, if the project is built with NativeScript Angular, the migration steps are:

1. Remove nativescript-dev-webpack:

npm uninstall -D nativescript-dev-webpack

2. Add @nativescript/webpack-ng as devDependency:

npm install -D @nativescript/webpack-ng