Fix all 20 hlint warnings across 5 source files

- Use newtype instead of data for single-field types (RouxConfig, ImportError)
- Replace maybe "" id with fromMaybe "" throughout
- Replace not (x `elem` ys) with x `notElem` ys
- Remove redundant brackets, redundant $, and eta-reduce lookupRecipe
- Use numeric underscore for 1_000_000

src/Roux/Html.hs

@@ -49,7 +49,7 @@ data SortMode
     deriving stock (Eq, Show)
 
 -- | Error type for the import pipeline.
-data ImportError = ImportError Text
+newtype ImportError = ImportError Text
     deriving stock (Eq, Show)
 
 -- ---------------------------------------------------------------------------
@@ -982,7 +982,7 @@ renderMethodSections sections = do
 isMethodSection :: Section -> Bool
 isMethodSection section =
     case sectionName section of
-        Just n -> not (T.toLower n `elem` ["ingredients", "ingredient"])
+        Just n -> T.toLower n `notElem` ["ingredients", "ingredient"]
         Nothing -> True
 
 -- | Extract (section name, body items) from a section for the method column.