fix rendering for both jekyll and github

[hchiam]

fix #64 (good and bad example rendering correctly for github but not for jekyll)
fix #66 (table rendering badly for both github and jekyll)

for screenshots of proof that the suggested fixes are guaranteed to work for both jekyll and github, see the comment at #66 (comment):
it mentions website cl-descriptions.html and github view of cl-descriptions.md

for convenience, you can see the raw code for cl-descriptions uses "``` {.good}" at https://raw.githubusercontent.com/google/eng-practices/refs/heads/master/review/developer/cl-descriptions.md

and here's what the table looks like now when the raw md code is viewed within vscode:

[hchiam]

basically:

what	renders correctly for jekyll	renders correctly for github
cl-descriptions	YES	YES
handling-comments	no (#64 (comment))	YES
small-cls	no (#66 (comment))	no (#66 (comment))

[hchiam]

Ready for review.