Add two generators to Faker::Science (#2175)

* Change write style to new version

* Add element state and subcategory to yaml file

* Add classes and tests for selement state and subcategory

* Update science.md file

* Add plasma to element state in .yml file

doc/default/science.md

@@ -5,5 +5,9 @@ Faker::Science.element #=> "Carbon"
 
 Faker::Science.element_symbol #=> "Pb"
 
+Faker::Science.element_state #=> "Liquid"
+
+Faker::Science.element_subcategory #=> "Reactive nonmetal"
+
 Faker::Science.scientist #=> "Isaac Newton"
 ```

lib/faker/default/science.rb

@@ -29,6 +29,32 @@ def element_symbol
         fetch('science.element_symbol')
       end
 
+      ##
+      # Produces the state of an element.
+      #
+      # @return [String]
+      #
+      # @example
+      #   Faker::Science.element_state #=> "Liquid"
+      #
+      # @faker.version next
+      def element_state
+        fetch('science.element_state')
+      end
+
+      ##
+      # Produces the subcategory of an element.
+      #
+      # @return [String]
+      #
+      # @example
+      #   Faker::Science.element_subcategory #=> "Reactive nonmetal"
+      #
+      # @faker.version next
+      def element_subcategory
+        fetch('science.element_subcategory')
+      end
+
       ##
       # Produces the name of a scientist.
       #