Implement spacing before/after for paragraphs

lib/notare/nodes/paragraph.rb

@@ -3,12 +3,14 @@
 module Notare
   module Nodes
     class Paragraph < Base
-      attr_reader :runs, :style
+      attr_reader :runs, :style, :spacing_before, :spacing_after
 
-      def initialize(runs = [], style: nil)
+      def initialize(runs = [], style: nil, spacing_before: nil, spacing_after: nil)
         super()
         @runs = runs
         @style = style
+        @spacing_before = spacing_before
+        @spacing_after = spacing_after
       end
 
       def add_run(run)