🔧 Add Config#with(**attrs) to make updated copies

lib/net/imap/config.rb

@@ -161,6 +161,23 @@ def update(**attrs)
         self
       end
 
+      # :call-seq:
+      #   with(**attrs) -> config
+      #   with(**attrs) {|config| } -> result
+      #
+      # Returns a shallow copy of +self+.  When provided with a block, yields
+      # the copy to the block and returns the block's result.
+      #
+      # If any keyword arguments are given, the copy will be updated with their
+      # values.
+      #
+      # If +self+ is frozen, the copy will also be frozen.
+      def with(**attrs)
+        copy = dup.update(**attrs)
+        copy.freeze if frozen?
+        block_given? ? yield(copy) : copy
+      end
+
       # :call-seq: to_h -> hash
       #
       # Returns all config attributes in a hash.