Merge pull request #215 from strukturag/ci-fix-readthedocs

CI: Pin dependencies to fix readthedocs build.

.github/dependabot.yml

@@ -9,3 +9,8 @@ updates:
     directory: "/"
     schedule:
       interval: "daily"
+
+  - package-ecosystem: "pip"
+    directory: "/docs"
+    schedule:
+      interval: "daily"

.readthedocs.yaml

@@ -11,3 +11,7 @@ build:
 
 mkdocs:
   configuration: mkdocs.yml
+
+python:
+  install:
+    - requirements: docs/requirements.txt

docs/requirements.txt

@@ -0,0 +1,4 @@
+sphinx==4.2.0
+sphinx_rtd_theme==1.0.0
+readthedocs-sphinx-search==0.1.1
+jinja2<3.1.0