docs: Add link to deprecation announcement to readme (#681)

* docs: Add link to deprecation announcement to readme

* Update base.txt

* Update test.yml

* Update README.rst

Author: fsbraun

.github/workflows/test.yml

@@ -27,7 +27,7 @@ jobs:
           dj50_cms41.txt,
         ]
         os: [
-          ubuntu-20.04,
+          ubuntu-latest,
         ]
         exclude:
           - python-version: 3.7

README.rst

@@ -5,6 +5,13 @@ django CMS Text CKEditor
 |pypi| |coverage| |python| |django| |djangocms| |djangocms4|
 
 
+.. warning::
+
+    This package will be deprecated on March 31, 2025 and not receive any updates thereafter. 
+    See the `deprecation announcement <https://www.django-cms.org/en/blog/2024/12/13/deprecation-announcement-djangocms-text-ckeditor-to-be-replaced-by-djangocms-text-in-q1-2025/>`_. 
+    Use `djangocms CMS Text <https://github.com/django-cms/djangocms-text>`_ as an alternative.
+
+
 .. note::
 
         Version 5 of this package does not include a move to CKEditor version 5

tests/requirements/base.txt

@@ -1,7 +1,7 @@
 # requirements from setup.py
 django-filer>=1.4.0, <3.2.0
 djangocms-picture>=2.1.0
-djangocms-link>=2.2.1
+djangocms-link>=2.2.1,<5
 django-polymorphic>=2.0.3
 Pillow
 html5lib>=0.999999999