doc: fixed links to respective GitHub issues page in CONTRIBUTING.md

[kumarlokesh]

Thank you for submitting this pull request! We really appreciate you spending the time to work on these changes.

What is the motivation?

• Couple of links for GitHub issue specified in the documentation aren't
  linked to the repository's issues page.
• They redirect to https://github.com/surrealdb/surrealdb/blob/main/issues,
  which gives a 404 - page not found message.

What does this change do?

Fixed links to the repository's GitHub issues page in the documentation.

What is your testing strategy?

Write your test plan here. Please provide us with clear instructions on how you verified your changes work.

Is this related to any issues?

N/A.

Does this change need documentation?

If this pull request requires changes, updates, or improvements to the documentation, then add a corresponding issue on the docs.surrealdb.com repository, and link to it here.

• No documentation needed
• Feat(docusaurus): Adds styling, theming and menus docs.surrealdb.com#1

Have you read the Contributing Guidelines?

• I have read the Contributing Guidelines