I believe this is the right place to submit this issue!
The correct way (AFAIK) to include a fenced code block (or anything) in a multi-line list item in markdown is by indenting it inbetween 3 and 7 spaces (I usually go for 4):
- A list
- with bullets
with multiple lines
- and fenced code blocks
```elixir
similarly indented
````
This (correctly) renders as:
-
A list
-
with bullets
with multiple lines
-
and fenced code blocks
However, at least in EXTRAs in my ex_doc projects, I do not get syntax highlighting for these indented code blocks.