markup for warnings

[pohly]

It would be useful to highlight paragraphs as info or warning (as in github/markup#887).

The proposal with embedded ‼️ in a table was tried, but didn't work with Sphinx (:bangbang: as rendered literally, #715 (comment)):

### Metrics support

:bangbang: | Metric support is an alpha feature. What data is provided may change.
:---: | :---

=>

Metrics support

‼️	Metric support is an alpha feature. What data is provided may change.

[pohly]

@intelkevinputnam : do you have an idea how to do this?

[intelkevinputnam]

I don't know of a way to make special characters work for both GitHub and Sphinx. Rather than the emoji, though, you could use **WARNING** or **NOTE**, or **!!**:

!!	Metric support is an alpha feature. What data is provided may change.

restructuredText has "Admonitions" which can be warnings, notes, etc. Markdown doesn't have them out of the box, though. Myst flavored markdown implements reST admonitions with this syntax:

```{admonition} Warning
This is Beta software.
```

In GitHub they look like this:

This is Beta software.

I could probably implement something that works like this in a couple of days. They work OK in GitHub (the notes would appear in code blocks) and would be proper "Notes" and "Warnings" in Sphinx output.

[pohly]

I think **WARNING** and **NOTE** inside a table are good enough, no need to implement any custom syntax support in the publishing pipeline.

@avalluri : agreed?

[avalluri]

@avalluri : agreed?

Yes.

[pohly]

This renders poorly in the docsite: https://cloudnative-k8sci.southcentralus.cloudapp.azure.com/job/pmem-csi/job/PR-760/Doc_20Site/docs/install.html#metrics-support

Let's stick with the current approach (**WARNING:** or **NOTE:** at the beginning of a paragraph).