test : added unit tests for ScrollToBottom component - #4

Summary of What Has Been Done

Created components/ScrollToBottom.test.tsx with unit tests covering:

• Correct aria-label on the button ("Scroll to bottom")
• Button is visible when scrolled near the top of the page
• Button scrolls to document bottom when clicked (calls window.scrollTo)
• Scroll target uses scrollHeight as the top value
• Fixed positioning and icon rendering

Mocked all framer-motion hooks (useScroll, useSpring, useTransform, useReducedMotion, AnimatePresence, motion.div, motion.circle) to prevent rendering dependencies on animation libraries.

Changes Made

• New file: components/ScrollToBottom.test.tsx

Impact it Made

Adds first unit test coverage for the ScrollToBottom component, ensuring the scroll-to-bottom navigation button correctly targets the document bottom.

Closes #8419.

Note: please assign this PR to the tmdeveloper007 account.