Build Lithops documentation

Install Sphinx and all plugins:

python3 -m pip install sphinx myst-parser sphinx_copybutton jupyter ipykernel nbsphinx sphinx_book_theme

Install Pandoc. For debian/ubuntu:
```
sudo apt install pandoc
```
Build the static HTML files:
```
make html
```
The documentation HTML files are located in the _build folder. Copy them to the website repo under docs folder:
```
rm -R ../../lithops-cloud.github.io/docs/*
cp -R _build/html/* ../../lithops-cloud.github.io/docs/
```
To clean build files run:
```
make clean
```

You can also use this Dockerfile to build the documentation using a Docker container.