feat: add attributes to createCustomer function

This commit includes enhancements in customer creation feature. Specifically, it modifies the
`createCustomer` function by adding a new parameter `$attributes` to handle attribute data during
customer creation process. Moreover, it introduces UI components to collect these attribute
details. Updates have been made to the associated form elements, button actions and display methods
to accommodate these changes. In addition, it makes considerable changes in the backend JavaScript
files to facilitate frontend changes and to meet compatibility.

There's also a change in error handling part where it replaces the `try-catch` block, which attempt
to get the standard address, with direct command. This assures the retrieval of the standard
address, if exists, else a new address will be created implicitly.

Finally, few general code improvements are done like changing usage of `var` to `const` or `let`
where necessary for better maintainability. A minor adjustment on window height property is also
made in `CustomerWindow.js` file.

Related: #68