Add copy button to the code blocks in docs

[greyli]

Update the mkdocs.yml to add a copy button to the code blocks in the documentation.

Ref: https://squidfunk.github.io/mkdocs-material/reference/code-blocks/#code-copy-button

[vimode]

Its me again! :) So can I try to include this feature in these docs?

Thank you.

[greyli]

Sure thing :)