add default ReadTheDocs configuration with graphviz installed

.readthedocs.yaml

@@ -1,12 +1,18 @@
+# yaml-language-server: $schema=https://raw.githubusercontent.com/readthedocs/readthedocs.org/refs/heads/main/readthedocs/rtd_tests/fixtures/spec/v2/schema.json
+# https://docs.readthedocs.io/en/stable/config-file/v2.html
+
 version: 2
 
 build:
   os: ubuntu-lts-latest
   tools:
-    python: mambaforge-latest
-
-conda:
-  environment: docs/rtd_environment.yaml
+    python: latest
+  apt_packages:
+    - graphviz
 
 sphinx:
+  builder: html
   configuration: docs/conf.py
+  fail_on_warning: true
+
+formats: []

{{ cookiecutter.package_name }}/.readthedocs.yaml

@@ -0,0 +1,25 @@
+# yaml-language-server: $schema=https://raw.githubusercontent.com/readthedocs/readthedocs.org/refs/heads/main/readthedocs/rtd_tests/fixtures/spec/v2/schema.json
+# https://docs.readthedocs.io/en/stable/config-file/v2.html
+
+version: 2
+
+build:
+  os: ubuntu-lts-latest
+  tools:
+    python: latest
+  apt_packages:
+    - graphviz
+
+python:
+  install:
+    - method: pip
+      path: .
+      extra_requirements:
+        - docs
+
+sphinx:
+  builder: html
+  configuration: docs/conf.py
+  fail_on_warning: true
+
+formats: []