Copy easily doc-as-code

Describe the problem to be solved

Sometimes I want to study the document as code.

So I retrieve the doc-as-python-code in the "Code view" panel.

But I have no easy way to copy this in one click or shortcut. It's tiresome for complex document with long structure.

Describe the solution you would like

Either (or both):

• CTRL+A would select ONLY the text within the code view, nothing else (not upper ribon, not side panel)
• A small button would allow to copy the whole text

Workaround until then:

• CTRL+A, then copy, then paste, then remove undesired data above the code itself
• Also, collapsing left/right panels reduces the surface of selected things

Somewhat related: https://github.com/gristlabs/grist-core/issues/900