* docs: add channel webpage setup guide
Step-by-step guide for channel owners to set up a web preview page:
enable the webpage in the app, copy the generated embed code, and host
the page. Includes the customizable data-* attributes and troubleshooting.
Linked from the user guide contents.
* docs: reorder channel webpage steps to recommended flow
Set up embedding first to build and test the page from any address,
and set the webpage URL last so the link is only shown to subscribers
once the page works. Also drop the incorrect 'Save and notify channel
subscribers' prompt references (that dialog only appears when leaving
with unsaved changes, not on Save).
sh
2df131bd05
