Pattern Creator: Preview a pattern while editing it

[ryelle]

Pulling this task out of #14.

The mockups have a preview button:

When clicked, it would show a dropdown like post previews #14 (comment)

I added the preview link as a possible location for both desktop/mobile preview as well as maybe theme switching.

Post screen example, probably something like this but instead of "Preview in a new tab", it could have some themes to apply. Maybe just the Twenty*s?

Option from mockups:

[ryelle]

@shaunandrews What do you expect happens when someone clicks the "View" text here? Should it be a separate preview, or the pattern details page?

[shaunandrews]

Ah, sorry for any confusion; There was a PR/issue in the Gutenberg repo that mentioned updating the "Preview" button to just "View," and my mockups reflect that change. But, the button just opens a menu that lets you adjust the editor's viewport size along with a link to open in a new tab:

I don't think we need to do anything different for the pattern editor immediately. We could definitely offer different themes to apply, but it seems out of scope for v1 of the directory.

[StevenDufresne]

@ryelle I think this can be closed since we implemented an "in-editor" preview tool in #115.