Disable deprecation warning if missing a command, and this not changed other behaviour. Issue #35 (#51)

Author: qichunren

lib/importmap/commands.rb

@@ -3,6 +3,10 @@
 
 class Importmap::Commands < Thor
   include Thor::Actions
+
+  def self.exit_on_failure?
+    false
+  end
 
   desc "pin [*PACKAGES]", "Pin new packages"
   option :env, type: :string, aliases: :e, default: "production"