Merge pull request #7 from Kijewski/pr-follow-up-6

Fix up #6: add missing file

.readthedocs.yaml

@@ -0,0 +1,12 @@
+# See https://docs.readthedocs.io/en/stable/config-file/v2.html for details
+
+version: 2
+
+build:
+  os: ubuntu-lts-latest
+  tools:
+    rust: latest
+  commands:
+    - mkdir -p $HOME/bin
+    - curl --location --silent --show-error --fail https://github.com/cargo-bins/cargo-quickinstall/releases/download/mdbook-0.4.40/mdbook-0.4.40-x86_64-unknown-linux-gnu.tar.gz | tar -xzvvf - -C $HOME/bin
+    - $HOME/bin/mdbook build book --dest-dir $READTHEDOCS_OUTPUT/html