Update doc CI to use mamba

Update docs conda env

Install the dev version of ipywidgets in readthedocs

.readthedocs.yaml

@@ -0,0 +1,19 @@
+version: 2
+
+build:
+  os: "ubuntu-22.04"
+  tools:
+    python: "mambaforge-4.10"
+python:
+  install:
+    - method: pip
+      path: ./python/ipywidgets
+conda:
+  environment: docs/environment.yml
+
+# python:
+#     version: 3.7
+#     install:
+#       - method: pip
+#         path: ./python/ipywidgets
+#       - requirements: docs/requirements.txt

docs/environment.yml

@@ -0,0 +1,24 @@
+name: docs
+channels:
+  - conda-forge
+  - nodefaults
+dependencies:
+  - bqplot
+  - empack
+  - ipykernel
+  - jupyter_client
+  - matplotlib
+  - nbsphinx
+  - numpy
+  - packaging
+  - pip
+  - python=3.10
+  - recommonmark
+  - scikit-image
+  - scikit-learn
+  - sphinx
+  - sphinx_rtd_theme
+  - pip:
+    - jupyterlite==0.1.0b9
+    - jupyterlite-sphinx
+    - jupyterlite-xeus-python