ct create: Listing available templates via `ct create -l`

lib/pve/cli/ct.rb

@@ -57,7 +57,11 @@ def cli_ct
       if %w[-h --help].include? template
         STDERR.puts "Usage: ct create TEMPLATE -h        # Shows template-related options"
         STDERR.puts "       ct create TEMPLATE [OPTIONS] # Creates a container"
+        STDERR.puts "       ct create -l                 # Listing available templates"
         exit 1
+      elsif %w[-l --list].include? template
+        STDERR.puts PVE::CTTemplate.constants.reject {|c|:Base==c}.map {|c|c.to_s.titlecase.dasherize.downcase}
+        exit 0
       end
       ctopts = {}
       OptionParser.new do |opts|