Address RTD deprecation for build-time Sphinx context injection (#4305)

* Set HTML baseurl and add RTD env vars to context

* Fix failing links

* suggestions from Arjun

Co-authored-by: Arjun Verma <[email protected]>

---------

Co-authored-by: Ferran Brosa Planella <[email protected]>
Co-authored-by: Arjun Verma <[email protected]>

CONTRIBUTING.md

@@ -153,9 +153,9 @@ All code requires testing. We use the [pytest](https://docs.pytest.org/en/stable
 
 We use following plugins for various needs:
 
-[nbmake](https://github.com/treebeardtech/nbmake&#41) : plugins to test the example notebooks.
+[nbmake](https://github.com/treebeardtech/nbmake/) : plugins to test the example notebooks.
 
-[pytest-xdist](https://pypi.org/project/pytest-xdist/&#41) : plugins to run tests in parallel.
+[pytest-xdist](https://pypi.org/project/pytest-xdist/) : plugins to run tests in parallel.
 
 If you have `nox` installed, to run unit tests, type
 

docs/conf.py

@@ -176,13 +176,21 @@
 html_sidebars = {"**": ["sidebar-nav-bs.html", "sidebar-ethical-ads.html"]}
 
 # For edit button
-html_context = {
-    "github_user": "pybamm-team",
-    "github_repo": "pybamm",
-    "github_version": "develop",
-    "doc_path": "docs/",
-}
+html_context.update(
+    {
+        "github_user": "pybamm-team",
+        "github_repo": "pybamm",
+        "github_version": "develop",
+        "doc_path": "docs/",
+    }
+)
+
+# Set canonical URL from the Read the Docs Domain
+html_baseurl = os.getenv("READTHEDOCS_CANONICAL_URL", "")
 
+# Tell Jinja2 templates the build is running on Read the Docs
+if os.getenv("READTHEDOCS") == "True":
+    html_context["READTHEDOCS"] = True
 
 # -- Options for HTMLHelp output ---------------------------------------------