docs: Update docstrings and readme

[apexDev37]

Description

This PR introduces minor patches to improve the docs by updating docstrings and README.md files to improve user experience.

Patches made:

• Enhance clarity of docstrings for learners.
• Fix typos and grammar errors.

Testing

N/A: This branch does not introduce functional code. No tests are to be run.

Additional

Codespell:

• The following Python package, codespell was used to find spelling errors in the repo and fix them interactively.

# NB: Warnings raised on `package-lock.json` can be safely ignored.
(trivia) ➜  trivia git:(docs-minor-patch) codespell .
./backend/README.md:9: virual ==> virtual, visual, viral
./frontend/README.md:123: cateogry ==> category
./frontend/package-lock.json:955: Ue ==> Use, Due
./frontend/package-lock.json:8175: bU ==> by, be, but, bug, bun, bud, buy, bum
./frontend/package-lock.json:10677: vise ==> vice
./frontend/package-lock.json:13627: vEw ==> view, vow, vex
./frontend/package-lock.json:15185: trough ==> through
./frontend/package-lock.json:15187: trough ==> through
./frontend/package-lock.json:15361: trough ==> through
./frontend/package-lock.json:15683: vise ==> vice
./frontend/package-lock.json:15685: vise ==> vice
./frontend/package-lock.json:17403: Ue ==> Use, Due
./frontend/package-lock.json:23245: bU ==> by, be, but, bug, bun, bud, buy, bum
./frontend/package-lock.json:25244: vise ==> vice
./frontend/package-lock.json:27596: vEw ==> view, vow, vex
./frontend/package-lock.json:28879: trough ==> through
./frontend/package-lock.json:28881: trough ==> through
./frontend/package-lock.json:29004: trough ==> through
./frontend/package-lock.json:29288: vise ==> vice
./frontend/package-lock.json:29290: vise ==> vice

Recommendation:
IMO, the following alternative TODO docstring should be used over the current one to provide students with clearer instructions.

This requires a Review or Input.

# Recommended.
"""@TODO: For each endpoint, write at least two tests:

- A success test to ensure it functions correctly with valid input.
- An error test to verify it handles invalid input as expected.
"""

# Current.
"""
@TODO:
Write at least one test for each endpoint for successful operation and for expected errors.
"""

Merge checklist:
Check off if complete or not applicable:

• Version bumped
• Changelog record added
• Documentation updated (not only docstrings)
• Fixup commits are squashed away
• Unit tests added/updated
• Manual testing instructions provided
• Noted any: Concerns, dependencies, migration issues, deadlines, tickets

[apexDev37]

⚡Fun fact: Former Udacity Alumni (Full-Stack Web Developer Nanodegree), glad to give back!