docs: fix broken admonitions (#2957)

* docs: fix broken admonitions

This commit ensures that the admonitions are in line with the new GFM
specifications (see
https://github.com/orgs/community/discussions/16925#discussioncomment-6506860).

* dev

---------

Co-authored-by: Alexandr <qwerty541zxc@gmail.com>

scripts/preview-theme.js

@@ -29,10 +29,10 @@ const FAIL_TEXT = `
 const THEME_CONTRIB_GUIDELINES = `
   \rHi, thanks for the theme contribution. Please read our theme [contribution guidelines](https://github.com/anuraghazra/github-readme-stats/blob/master/CONTRIBUTING.md#themes-contribution).
 
-  \r> **Warning**
+  \r> [!WARNING]\
   \r> Keep in mind that we already have a vast collection of different themes. To keep their number manageable, we began to add only themes supported by the community. Your pull request with theme addition will be merged once we get enough positive feedback from the community in the form of thumbs up (see [#1935](https://github.com/anuraghazra/github-readme-stats/issues/1935#top-themes-prs)). Remember that you can also support themes of other contributors that you liked to speed up their merge.
 
-  \r> **Note**
+  \r> [!NOTE]\
   \r> Also, note that if this theme is exclusively for your personal use, then instead of adding it to our theme collection, you can use card [customization options](https://github.com/anuraghazra/github-readme-stats#customization).
 `;
 const COLOR_PROPS = {