Improve the instructions regarding pandoc (#336)

I've also tried to make the developer documentation easier to discover

docs/index.rst

@@ -27,6 +27,11 @@ If you use the Circuit Knitting Toolbox in your research, please cite it accordi
 .. literalinclude:: ../CITATION.bib
    :language: bibtex
 
+Developer guide
+---------------
+
+The developer guide is located at `CONTRIBUTING.md <https://github.com/Qiskit-Extensions/circuit-knitting-toolbox/blob/main/CONTRIBUTING.md>`__ in the root of this project's repository.
+
 Contents
 --------
 

test/README.md

@@ -61,14 +61,18 @@ $ tox -e coverage
 
 ## Documentation environment
 
-The `docs` environment builds the [Sphinx] documentation locally.  If the build succeeds, it can be viewed by navigating to `docs/_build/html/index.html` in a web browser.
+The `docs` environment builds the [Sphinx] documentation locally.
 
-To run:
+For the documentation build to succeed, [pandoc](https://pandoc.org/) must be installed.  Pandoc is not available via pip, so must be installed through some other means.  Linux users are encouraged to install it through their package manager (e.g., `sudo apt-get install -y pandoc`), while macOS users are encouraged to install it via [Homebrew](https://brew.sh/) (`brew install pandoc`).  Full instructions are available on [pandoc's installation page](https://pandoc.org/installing.html).
+
+To run this environment:
 
 ```sh
 $ tox -e docs
 ```
 
+If the build succeeds, it can be viewed by navigating to `docs/_build/html/index.html` in a web browser.  Specifically, run `pwd` in the same terminal in which you built the docs, then copy that location and paste it in your web browser.  You should see a directory listing there.  If not, prepend `file://` to the path and try again.  Once you see the directory listing, click on `docs`, then `_build`, then `html`, and then finally `index.html` to view the documentation.
+
 [tox]: https://github.com/tox-dev/tox
 [`tox.ini`]: ../tox.ini
 [mypy]: https://mypy.readthedocs.io/en/stable/