Fix: fixed the copy icon of copy_block in CodeBlock.tsx

[a-khushal]

PR Fixes:

• 1 added copy svg
• 2 made visibility of copy icon responsive

Resolves #[Issue Number if there]

Checklist before requesting a review

• [x] I have performed a self-review of my code
• [x] I assure there is no similar/duplicate pull request regarding same issue Here is a screen recording of the changes: Screencast from 04-05-24 02:38:58 PM IST.webm