Add links to docs from mode descriptions

[amedina]

Once the user dismisses the welcome banner there is no persistent links back to the site guiding users to documentation sources. Adding links back to development workflow guidance will help users when engaging with the template mode settings.

[swissspidy]

I'd suggest using sprintf() here and using placeholders for the actual URLs. It's a general best practice thing because this way, if the URLs to the documentation change at any point for some reason, the strings don't have to change, meaning all the translations will still be valid.

Example:

/* translators: %s: URL to the documentation. */
$native_description = sprintf( __( 'Integrates AMP as the framework for your site by using the active’s theme templates and styles to render AMP responses. This means your site is <b>AMP-first</b> and your canonical URLs are AMP! Depending on your theme/plugins, a varying level of <a href="%s">development work</a> may be required.', 'amp' ), 'https://amp-wp.org/documentation/developing-wordpress-amp-sites/' );