Default styling for rx.upload

[AmanSal1]

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Type of change

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• Bug fix (non-breaking change which fixes an issue)
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After these steps, you're ready to open a pull request.

a. Give a descriptive title to your PR.
Adding a default styling to the rx.upload method 

b. Describe your changes.
I have implemented a logic to provide default styling. Whenever a user employs rx.upload, default styling will be applied if 
not explicitly mentioned. Users can override these defaults with custom styles if desired.

c. Put `closes #XXXX` in your comment to auto-close the issue that your PR fixes (if such).
Fixes : #2967 

[AmanSal1]

@picklelo I have implemented logic to apply default styling, and I would like you to review it. I have verified that users can directly override the existing default styles. However, I haven't written any test cases yet. Once you confirm, we can proceed to add the necessary test cases .

[Lendemor]

We merged #3035 doing styling for rx.upload