follow-up #18013 - inline syntax highlighting

[a-mr]

This should be the final PR for enabling inline highlighting in standalone rst files.

[timotheecour]

so when can i use

```nim
some code...
```

(which brings us closer to markdown, which is good) ? can any instead of

.. code-block:: cmd
  some code...

be replaced or are there conditions?

[a-mr]

always, they are equivalent. You can write ```cmd and ```nim and any other language.

However note bug 22 from #17340. When it's resolved we can convert to using this Markdown style as a unified style in this repo just as you wanted.

There is 1 thing that I don't like about Markdown style: addition of those spaces at the beginning of lines. It would be good to visually distinguish code lines in documentation by additional indentation without adding them into final document.

I'd prefer to pass the code block between ``` through dedent. WDYT?

(That does not comply to Markdown spec but it seems as a reasonable default)

[a-mr]

Actually I found in the specification

https://spec.commonmark.org/0.29/#fenced-code-block

If the leading code fence is indented N spaces, then up to N spaces of indentation are removed from each line of the content (if present).

And this does actually work in Github:

  ```
  some code
  ```

some code

[timotheecour]

cool;

can you explain 22?
this seems to render fine with nim doc, doesn't it?

proc main*()=
  ##[
  foo1:
  ```nim
  echo 1
  ```
  * foo2:
    ```nim
    echo 2
    ```
  ]##

main()

[a-mr]

add e.g. two additional spaces as indentation before echo 1 or echo 2. And they will disappear.

[a-mr]

filed bug 23 in the same place :-)