Make copy button icon permanent and strip its white space

[cjsha]

This PR does two things: makes copy icon appear permanently (instead of only appearing when hovering over the workflow) and strips white space from the copy button. I'm not sure if y'all want this, but I think it's worth considering. We will probably make these additions in our files in the open ephys docs if you don't here.

Make copy button permanent

Currently the copy button icon only appears when the cursor hovers over the workflow container. I propose that the copy button appears permanently. This is meant to address the first item in the bullet point of this issue. This accomplished by 3e90c1a.

Strip white space from copy button

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The copy button clickable area extends from the clipboard button to the left. Any whitespace contained by an HTML <pre> tag is rendered. Not sure if this was intentional. I propose removing that white space. This is accomplished by 7a2580b.

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[glopesdev]

@cjsha thanks for the contribution. I think this could be split into two different PRs, one visual and the other functional.

Let's discuss this at the next dev club. The reason why we kept the copy button behavior on hover is for consistency with all the other code blocks, e.g. python / c#. Not sure if your PR changes the behavior also for those boxes.

As for the visual change, again as long as the change is to improve consistency with the other blocks I would be happy with it.

[cjsha]

3e90c1a changes behavior of the code block and is probably inconsistent with how other code blocks work.
7a2580b basically just changes the clickable area for the copy button. This might be important, for example, if you want to put a button next to it (like a download button), but I suppose that's also inconsistent with other code blocks which I feel like usually have clipboard-copy buttons and no download buttons.