Updated welcome page buttons styling from square to rounded

[shivamb11]

Fixes: #27468

Changed buttons styling and added hover effect on them for improved user experience.

Checklist

• Tests written for new code (and old code if feasible).
• New or updated public/exported symbols have accurate TSDoc documentation.
• Linter and other CI checks pass.
• Sign-off given on the changes (see CONTRIBUTING.md).

Before:

After:

[florianduros]

Thanks for you contribution.
The changes are design related, we will wait for the opinion of the design team on it.

[shivamb11]

Sure thing. Glad to have worked on it.

[Hinaichigo]

Rounded doesn't mean necessarily better user experience. Round buttons and elements can be aesthetically distracting.

[CLAassistant]

Thank you for your submission! We really appreciate it. Like many open source projects, we ask that you sign our Contributor License Agreement before we can accept your contribution.
_{You have signed the CLA already but the status is still pending? Let us recheck it.}