ui/project_form: Improve file handling in UI

[jayanth-kumar-morem]

• Enhance file input handling in the UI to avoid losing selected files when adding new inputs.
• Introduce a selectedFiles array to store and manage selected files.
• Display selected files in the UI with additional features, including a delete button.
• Update the removeFile function to correctly remove files from both the UI and the selectedFiles array.

Fixes: #991

UI Updates

https://github.com/nexB/scancode.io/assets/64846852/4d615d1a-1128-4633-9728-34153f6bc564

[tdruez]

@jayanth-kumar-morem I've noticed an issue while reviewing this PR, to reproduce:

• Drag and drop a file into the form, then drag and drop it again. The file is duplicated in the list. Note that this does not happen with the "Click" to select file.