🔖(minor) release 3.1.0

Added:
- 🚩(backend) add feature flag for the footer
- 🔧(backend) add view to manage footer json
- ✨(frontend) add custom css style
- 🚩(frontend) conditionally render AI button only
  when feature is enabled

Changed:
- 🚨(frontend) block button when creating doc

Fixed:
- 🐛(back) validate document content in serializer
- 🐛(frontend) fix selection click
  past end of content

src/backend/pyproject.toml

@@ -7,7 +7,7 @@ build-backend = "setuptools.build_meta"
 
 [project]
 name = "impress"
-version = "3.0.0"
+version = "3.1.0"
 authors = [{ "name" = "DINUM", "email" = "dev@mail.numerique.gouv.fr" }]
 classifiers = [
     "Development Status :: 5 - Production/Stable",