Minor typos/fixes to autoloading guide

@fxn Great job with the guide, I read it all! Yeah!

Some paragraphs might be restructured, but I'll leave that to you
since you are currently working on it. This commit only includes
some minor typos and commas that in my opinion clarify the reading.

[ci skip]
Merge pull request #18043 from claudiob/minor-autoloading-guides-fixes

Minor typos/fixes to autoloading guide