Update README.md to ensure embedded yaml passes yamllint

[cooljeanius]

When I tried copying the yaml snippet from the README into a fresh workflow, I got the following warnings from yamllint when I checked it with it:

$ yamllint .github
.github/workflows/alt-text-accessibility-bot.yml
  3:1       warning  truthy value should be one of [false, true]  (truthy)
  3:4       error    trailing spaces  (trailing-spaces)
  19:1      error    trailing spaces  (trailing-spaces)
  27:56     warning  too few spaces before comment: expected 2  (comments)

I'm not sure how to fix the first of those, but this PR fixes the other 3. It also updates the version number listed.

[JoyceZhu]

Thank you for the contribution. Please feel free to add yourself to our Contributors section!

[cooljeanius]

Thank you for the contribution. Please feel free to add yourself to our Contributors section!

OK I think I did it correctly; it took me a bit to figure out...