Incorporate copy button for shell script and other code snippets in the docs

[krishnakumarg1984]

mkdocs for material comes with a new copy code button that makes it easy to copy code such as those given in the example job scripts page here.

Achieving this requires just a simple yaml config update as per their docs here (not sure from which version of mkdocs was that feature incorporated).

[ikirker]

I have a half-memory that suggests I might have deliberately left this or a feature like this off on the instruction of the accessibility folks because it made the page incomprehensible to screen readers (via nested buttons with repeated, undifferentiated buttons that each got read out separately?).

If someone's enabling this, please check what it sounds like.