Migrate to pydata sphinx

Dockerfile

@@ -12,9 +12,7 @@ RUN apt-get update && apt-get install -y \
     # Optional NIFTy dependencies
     python3-mpi4py python3-matplotlib \
   # more optional NIFTy dependencies
-  && pip3 install ducc0 \
-  && pip3 install finufft \
-  && pip3 install jupyter \
+  && pip3 install ducc0 finufft jupyter sphinx pydata-sphinx-theme \
   && rm -rf /var/lib/apt/lists/*
 
 # Set matplotlib backend

docs/source/conf.py

 import nifty7
 
+needs_sphinx = '3.2.0'
+
 extensions = [
     'sphinx.ext.napoleon',  # Support for NumPy and Google style docstrings
     'sphinx.ext.imgmath',  # Render math as images
@@ -26,7 +28,7 @@ language = None
 exclude_patterns = []
 add_module_names = False
 
-html_theme = "sphinx_rtd_theme"
+html_theme = "pydata_sphinx_theme"
 html_logo = 'nifty_logo_black.png'
 
 exclude_patterns = [

docs/source/ift.rst

-IFT -- Information Field Theory
-===============================
+Information Field Theory
+========================
 
 Theoretical Background
 ----------------------

docs/source/volume.rst

-Discretisation and Volume in NIFTy
-==================================
+Discretisation and Volume
+=========================
 
 .. note:: Some of this discussion is rather technical and may be skipped in a first read-through.