Fix warning badge in README

Author: jamesmbaazam

README.Rmd

@@ -26,6 +26,7 @@ knitr::opts_chunk$set(
 
 
 > [!WARNING]
+
 `{bpmodels}` is now *retired and will no longer be maintained*. We recommend using [`{epichains}`](https://github.com/epiverse-trace/epichains) instead. If you need help converting your code to use `{epichains}`, please [open a discussion on epichains](https://github.com/epiverse-trace/epichains/discussions).
 
 ```{r setup, include=FALSE}