docs: update citation format and add total downloads badge in README and citation documentation

Author: orabe

README.rst

@@ -9,14 +9,17 @@ CaliBrain
    :target: https://pypi.org/project/calibrain/
    :alt: Supported Python versions
 
-.. .. image:: https://static.pepy.tech/badge/calibrain
-..    :target: https://pepy.tech/projects/calibrain
-..    :alt: Total downloads
-.. 
-.. .. image:: https://readthedocs.org/projects/calibrain/badge/?version=latest
-..    :target: https://calibrain.readthedocs.io/en/latest/
-..    :alt: Documentation status
+.. image:: https://static.pepy.tech/badge/calibrain
+   :target: https://pepy.tech/projects/calibrain
+   :alt: Total downloads
 
+.. image:: https://readthedocs.org/projects/calibrain/badge/?version=latest
+   :target: https://calibrain.readthedocs.io/en/latest/
+   :alt: Documentation status
+
+.. image:: https://github.com/braindatalab/CaliBrain/actions/workflows/docs-check.yml/badge.svg
+   :target: https://github.com/braindatalab/CaliBrain/actions/workflows/docs-check.yml
+   :alt: Documentation build
 .. image:: https://img.shields.io/github/license/braindatalab/CaliBrain
    :target: https://github.com/braindatalab/CaliBrain/blob/main/LICENSE
    :alt: License

docs/source/index.rst

@@ -16,9 +16,9 @@ CaliBrain
    :target: https://pypi.org/project/calibrain/
    :alt: Supported Python versions
 
-.. .. image:: https://static.pepy.tech/badge/calibrain
-..    :target: https://pepy.tech/projects/calibrain
-..    :alt: Total downloads
+.. image:: https://static.pepy.tech/badge/calibrain
+   :target: https://pepy.tech/projects/calibrain
+   :alt: Total downloads
 
 .. image:: https://img.shields.io/github/license/braindatalab/CaliBrain
    :target: https://github.com/braindatalab/CaliBrain/blob/main/LICENSE