Blueprint: Add "use blueprint" page

I’ve created a Blueprint, and I want some less-technical developers to use it to create stacks.

For each blueprint, please create a page which contains the “create stack” UI.

Example URL: /blueprint/{name}-{id}/create

Currently, this UI is only found on the blueprint details page, which is ugly and overwhelming for non-advanced Spacelift users. It additionally requires you to find and click the “Create Stack” button, which is small and difficult to locate.