Changed the formatting in several scripts related to handling currency, specifically in
Currency.js, Select.js, SelectItem.js, Search.js, Window.js, AccountingCurrencyDiffers.js,
AllowedCurrencies.js, CurrencyList.js, CurrencyWindow.js, and Import.js. This ensures improved
readability and consistency in the code structure. These changes involved adjustments to the
spacing and indentation used.

This commit introduces several changes in bin/Currency.js to make the code more readable and
consistent:

1. Improved function declaration style: Rather than using `function(arg1, arg2) { .. }`, we now use
`function (arg1, arg2) { .. }` for better style consistency.
2. Cleaned up unnecessary whitespace: Removed redundant lines to make the code cleaner and more
readable.
3. Added a new function: Introduced a new function `getDefaultCurrency()` for fetching the default
system currency. This asynchronous function returns a Promise that resolves to the code of the
default currency.

feat: user currency -> the user can now have his own currency, so he can use the exchange rate to display the price in his currency.

- Default Currency ist im Template über eine JS Constante erreichbar
- Ajax Currency calculation