Release v3.0.3 (#2719)

* Bump version
* Bump pyright version and fix newly reported issues
* Update release notes
* Fix typos, extend release process desc
* Add readthedocs configuration file v2
* Fix Dockerfile.citus files

.readthedocs.yaml

@@ -0,0 +1,21 @@
+# .readthedocs.yaml
+# Read the Docs configuration file
+# See https://docs.readthedocs.io/en/stable/config-file/v2.html for details
+
+# Required
+version: 2
+
+# Set the version of Python and other tools you might need
+build:
+  os: ubuntu-22.04
+  tools:
+    python: "3.11"
+
+# Build documentation in the docs/ directory with Sphinx
+sphinx:
+  configuration: docs/conf.py
+
+formats:
+  - epub
+  - pdf
+  - htmlzip