Added deprecation message.

README.md

@@ -1,11 +1,24 @@
-
 <p align="center">
   <a title="'Test' workflow Status" href="https://github.com/ghdl/setup-ghdl-ci/actions/workflows/test.yml"><img alt="'test' workflow Status" src="https://img.shields.io/github/actions/workflow/status/ghdl/setup-ghdl-ci/test.yml?branch=master&longCache=true&style=flat-square&label=Test&logo=GitHubActions&logoColor=fff"></a><!--
   -->
 </p>
 
 # GitHub Action to setup [GHDL](https://github.com/ghdl/ghdl)
 
+> [!CAUTION]
+> This GitHub Action has been deprecated in favor of [setup-ghdl](https://github.com/ghdl/setup-ghdl).
+> ```yml
+> jobs:
+>   GHDL-on-Ubuntu:
+>     runs-on: ubuntu-24.04
+>     steps:
+>       - name: Run VHDL Simulation
+>         uses: ghdl/setup-ghdl@v1
+>         with:
+>           version: nightly
+>           backend: mcode
+> ```
+
 **setup-ghdl-ci** is a JavaScript GitHub Action (GHA) to setup GHDL using [nightly](https://github.com/ghdl/ghdl/releases/tag/nightly) release assets. Latest packages are retrieved and installed along with required dependencies, to enable testing of VHDL designs in Continuous Integration (CI) workflows.
 
 Currently, GitHub Actions workflow tasks running on Ubuntu or Windows are supported only. Precisely [environments](https://github.com/actions/virtual-environments#available-environments) `ubuntu-20.04`, `ubuntu-22.04`, `ubuntu-24.04`|`ubuntu-latest`, `windows-2019` or `windows-2022`|`windows-latest` can be used.