Move core.loadPlugins function into plugin package

[Dominik Braun]

In core/build.go, there's a small function called loadPlugins. This function returns a simple map containing all plugin keys and a corresponding function that loads the plugin - i.e. it simply returns an instance.

verless/core/build.go

Lines 301 to 311 in 16673b1

 // loadPlugins returns a map of all available plugins. Each entry 
 // is a function that returns a fully initialized plugin instance. 
 func loadPlugins(cfg *config.Config, fs afero.Fs, outputDir string) map[string]func() Plugin { 
  
 	plugins := map[string]func() Plugin{ 
 		"atom": func() Plugin { return atom.New(&cfg.Site.Meta, fs, outputDir) }, 
 		"tags": func() Plugin { return tags.New() }, 
 	} 
  
 	return plugins 
 } 

I have no idea why this function is inside the core package. It should be inside the plugin package. The best way would be to just move it into a new file plugin/plugin.go. The function signature can remain unchanged.

[Vitalii Ananichev]

Hey @dominikbraun, I'll take this one

[Vitalii Ananichev]

@dominikbraun, could you please review PR #211