Add retirement badge and note in README

README.Rmd

@@ -16,13 +16,18 @@ knitr::opts_chunk$set(
 # _bpmodels_: Methods for simulating and analysing the size and length of transmission chains from branching process models
 
 <!-- badges: start -->
+[![Lifecycle: retired](https://img.shields.io/badge/lifecycle-retired-orange.svg)](https://lifecycle.r-lib.org/articles/stages.html#retired)
 ![GitHub R package version](https://img.shields.io/github/r-package/v/epiverse-trace/bpmodels)
 [![R-CMD-check](https://github.com/epiverse-trace/bpmodels/actions/workflows/R-CMD-check.yaml/badge.svg)](https://github.com/epiverse-trace/bpmodels/actions/workflows/R-CMD-check.yaml)
 [![codecov](https://codecov.io/github/epiverse-trace/bpmodels/branch/main/graph/badge.svg)](https://app.codecov.io/github/epiverse-trace/bpmodels) 
 ![GitHub contributors](https://img.shields.io/github/contributors/epiverse-trace/bpmodels)
 [![License: MIT](https://img.shields.io/badge/License-MIT-yellow.svg)](https://opensource.org/license/MIT/)
 <!-- badges: end -->
 
+## Note
+
+> `{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}
 knitr::opts_chunk$set(echo = TRUE)
 ```