Iterate on blog post flow

[psrpinto]

This PR iterates on the blog post flow.

Note that the API calls are not correct yet, this PR just does the minimum so that the flow is in place, I will make the correct API calls in the next PR. This means that currently, the preview does not show the title the user selected, for example, it just shows an empty post page.

Summary of changes

• Make it possible to ask the content script what the current URL is
• Make it possible to make POST requests to the API, through the createPost() and updatePost() methods of ApiClient. These methods are not fully implemented yet, I will do so in the next PR.
• Add PlaygroundClient to the session context, so that it's available everywhere.
• Call the WP REST API at the start of the Import Blog flow, to create an empty post.
• Make Playground automatically navigate to the page of said post.
• As the user selects elements (title, date, etc), we make requests to the API to update the post, and refresh the page in playground. (this is not visible yet as the API calls are not correct).

Screen capture

Note how Playground navigates to the page of the post.

Screen.Recording.2024-09-18.at.17.51.21.mov

[ashfame]

LGTM! 👍