docs: fix tutorial path with inline templates

Replace stale `cargo install sukr` with install-from-source.
Replace Step 4 dead-end with inline base.html, page.html,
and content/default.html templates. Add "View your site"
completion step. Improve Next Steps with reading-order context.

docs/content/_index.md

@@ -21,7 +21,9 @@ Most static site generators punt rich content to the browser. sukr doesn't.
 
 ```bash
 # Install
-cargo install sukr
+git clone https://github.com/nrdxp/sukr
+cd sukr
+cargo install --path .
 
 # Create site structure
 mkdir -p content templates static