GH 801: add copy button for code blocks

[aloks98]

Checklist

Please note that in case of below checklist not updated accordingly, the maintainers have the right to immediately close your pull request.

• [x] You created a branch from dev branch.
• [x] You PR is raised on dev branch and not onmaster.
• [x] Blog follows Blog Guidelines.
• [x] You have read the Contribution Guidelines before creating this PR.
• [ ] Checked for any duplicate blog entry.
• [ ] Checked for all grammatical errors in the blog.
• [ ] You have not published the blog content anywhere else on the internet on platforms like medium, dev.to etc.
• [ ] The content is not copy-pasted from anywhere else on the Internet.

Description of change

Fix #801