cli: add config and images command

Extends the existing zot CLI to add commands for listing all images and
their details on a zot server.
Listing all images introduces the need for configurations.

Each configuration has a name and URL at the least. Check 'zot config
-h' for more details.

The user can specify the URL of zot server explicitly while running the
command or configure a URL and pass it directly.

Adding a configuration:
zot config add aci-zot <zot-url>

Run 'zot config --help' for more.

Listing all images:
zot images --url <zot-url>

Pass a config instead of the url:
zot images <config-name>

Filter the list of images by image name:
zot images <config-name> --name <image-name>

Run 'zot images --help' for all details

- Stores configurations in '$HOME/.zot' file

Add CLI README

pkg/cli/root.go

@@ -19,7 +19,7 @@ func metadataConfig(md *mapstructure.Metadata) viper.DecoderConfigOption {
 	}
 }
 
-func NewRootCmd() *cobra.Command {
+func NewRootCmd(configPath string) *cobra.Command {
 	showVersion := false
 	config := api.NewConfig()
 
@@ -96,6 +96,10 @@ func NewRootCmd() *cobra.Command {
 
 	rootCmd.AddCommand(serveCmd)
 	rootCmd.AddCommand(gcCmd)
+
+	rootCmd.AddCommand(NewConfigCommand(configPath))
+	rootCmd.AddCommand(NewImageCommand(NewImageSearchService(), configPath))
+
 	rootCmd.Flags().BoolVarP(&showVersion, "version", "v", false, "show the version and exit")
 
 	return rootCmd