Fix: Conditional Attribute Binding for the multiple Attribute in the File Selector Fragment

[Ludy87]

Description

Previous State:
The multiple attribute in the <input> element of the file selector fragment was statically defined, meaning it was either always present or always absent, regardless of the actual requirement. There was no way to dynamically set this attribute based on the multiple variable managed in the JavaScript code.

Fix:
This fix introduces conditional binding for the multiple attribute using Thymeleaf, based on the value of the multiple variable in the JavaScript. As a result, the attribute is only added if multiple is set to true, making the file selector's behavior dynamic and more flexible.

Checklist:

• I have read the Contribution Guidelines
• I have performed a self-review of my own code
• I have commented my code, particularly in hard-to-understand areas
• My changes generate no new warnings

Contributor License Agreement

By submitting this pull request, I acknowledge and agree that my contributions will be included in Stirling-PDF and that they can be relicensed in the future under the MPL 2.0 (Mozilla Public License Version 2.0) license.

(This does not change the general open-source nature of Stirling-PDF, simply moving from one license to another license)

[Frooodle]

:o oops