Docs: Update docs with typo fixes

This merge request fixes some small typos, adds information on editing an episode, and fixes Notes in the following pages:

• Fix "Notes" paragraph in episodes.mdx and the Website Overview page index.mdx
• Fix typo in Manage your instance / users.mdx: Add missing t from the word "the"
• Fix typo in Manage your instance / podcast.mdx - remove n from "ration" should be "ratio"
• Add missing @ symbol to the podcast handle examples in Website overview index.mdx
• Add paragraph explaining how to edit an episode prior to or after publishing an episode

Please let me know if I need to update anything if I did anything incorrectly.

Thanks!

docs/src/content/docs/en/user-guide/instance/podcast.mdx

@@ -98,7 +98,7 @@ To learn more about Fediverse integration, visit the
 ### Podcast banner
 
 Upload a banner image to be displayed at the top of your podcast's home page.
-The banner must have a 3:1 ration and be at least 1500px wide.
+The banner must have a 3:1 ratio and be at least 1500px wide.
 
 ### Premium