[WIP]: Add copy functionality to the editor

[dixita0607]

• Add "Copy to clipboard" button beside Format

• Reason: A few requests to directly open the embedded dartpad in new tab. After reading about the usage of git gists, it seemed difficult to right away provide it. The copy seems a low hanging fruit and an improved UI.
• More details lightweight dartpad embedding #2702 (comment)

TODO:

• Tests for this feature

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[dixita0607]

@devoncarew,

If this feature looks good, I will add all the tests and push a few new commits. Wanted to know about team's input on this.

[devoncarew]

Thanks for the PR! My guess is that we want to do everything we can to minimize the amount of UI that we're floating aobve the editing area (up to and including somehow removing some of the current FAB buttons). Perhaps there's somewhere else we could put the copy- to-clipboard functionality? Though I'm not 100% that if would be a frequent user action.

But generally, the review for this PR + feature would be from @johnpryan.

[dixita0607]

My guess is that we want to do everything we can to minimize the amount of UI that we're floating aobve the editing area (up to and including somehow removing some of the current FAB buttons)

For this, I have something like this in mind. Refer this as a wireframe, The final implementation will have proper styling.

Though I'm not 100% that if would be a frequent user action

It won't be a frequent one but sure is useful for tutors or people who want to open the embedded dartpads in new tab. I see that is not a straight forward implementation so this UX would be easier for users.

Ref: flutter/website#12283

What do you think?