Add a validation rule to make sure releases are properly ordered

According to the contributing guide (https://github.com/endoflife-date/endoflife.date/blob/master/CONTRIBUTING.md) releases must be ordered from the newest (on top of the list) to the lowest. This updates product-data-validator to enforce that rule.

Close #3960.

_plugins/product-data-validator.rb

@@ -121,6 +121,7 @@ def self.validate(product)
     error_if.is_not_an_array('auto')
     error_if.is_not_an_array('identifiers')
     error_if.is_not_an_array('releases')
+    error_if.not_ordered_by_release_cycles('releases')
 
     for release in product.data['releases']
       error_if = Validator.new(product, release)
@@ -244,6 +245,24 @@ def is_not_a_boolean_nor_a_string(property)
       end
     end
 
+    def not_ordered_by_release_cycles(property)
+      releases = @data[property]
+
+      previous_release_cycle = nil
+      previous_release_date = nil
+      releases.each do |release|
+        release_cycle = release['releaseCycle']
+        release_date = release['releaseDate']
+
+        if previous_release_date and previous_release_date < release_date
+          declare_error(property, release_cycle, "expecting release to be before #{previous_release_cycle}")
+        end
+
+        previous_release_cycle = release_cycle
+        previous_release_date = release_date
+      end
+    end
+
     def is_url_invalid(property)
       # strip is necessary because changelogTemplate is sometime reformatted on two lines by latest.py
       url = @data[property].strip