message: Remove ES6 'const' from bn locale
  When using locales webpack/uglify fails with
  ```
  [webpack] errors:
  app/6ec78c4b5b.js from UglifyJs
  Unexpected token: keyword (const) [../wa-storybook/node_modules/date-fns/esm/locale/bn/_lib/localize/index.js:141,0][app/6ec78c4b5b.js:98206,2]
  ```
  This patch changes const to var.
diff: @@ -138,7 +138,7 @@ function dateOrdinalNumber (number, localeNumber) {
  function ordinalNumber (dirtyNumber, dirtyOptions) {
  var number = localize.localeToNumber(dirtyNumber)
  var localeNumber = localize.numberToLocale(number)
  - const { unit } = dirtyOptions
  + var unit = dirtyOptions.unit
  if (unit === 'date') {
  return dateOrdinalNumber(number, localeNumber)
  