Add missing doc comments

Author: adamreeve

parquet/src/column/page.rs

@@ -90,10 +90,12 @@ impl Page {
         }
     }
 
+    /// Returns whether this page is any version of a data page
     pub fn is_data_page(&self) -> bool {
         matches!(self, Page::DataPage { .. } | Page::DataPageV2 { .. })
     }
 
+    /// Returns whether this page is a dictionary page
     pub fn is_dictionary_page(&self) -> bool {
         matches!(self, Page::DictionaryPage { .. })
     }