docs: add gitlab compatibility

Signed-off-by: Cédric OLIVIER <cedric3.olivier@orange.com>

README.md

@@ -280,3 +280,7 @@ It is bound to the `publish` stage, applies only on tags and uses the following
 | `DOCS_DIRECTORY`         | Directory containing docs source                                                       | `docs`                            |
 | `DOCS_BUILD_DIR`         | Output build directory for documentation                                               | `public`                          |
 | `DOCS_MAKE_ARGS`         | Args of make command                                                                   | `html BUILDDIR=${DOCS_BUILD_DIR}` |
+
+## Gitlab compatibility
+
+:information_source: This template is actually tested and validated on GitLab Community Edition instance version 13.12.11