add discussion in index

Author: tmigot

docs/src/index.md

@@ -93,6 +93,13 @@ TODO after CUTEst.jl and NLPModelsJuMP are updated.
 
 This content is released under the [MPL2.0](https://www.mozilla.org/en-US/MPL/2.0/) License.
 
+# Bug reports and discussions
+
+If you think you found a bug, feel free to open an [issue](https://github.com/JuliaSmoothOptimizers/NLPModelsTest.jl/issues).
+Focused suggestions and requests can also be opened as issues. Before opening a pull request, start an issue or a discussion on the topic, please.
+
+If you want to ask a question not suited for a bug report, feel free to start a discussion [here](https://github.com/JuliaSmoothOptimizers/Organization/discussions). This forum is for general discussion about this repository and the [JuliaSmoothOptimizers](https://github.com/JuliaSmoothOptimizers), so questions about any of our packages are welcome.
+
 ## Contents
 
 ```@contents