Script files
In order to create the reStructuredText files the following files need to be installed on your system.
For extracting information from Godot
Collector.gd: Scans your Godot script files and extracts the required information
ReferenceCollector.gd: A setup file for determining what Collector.gd scans.
ReferenceCollectorCLI.gd: A command line tool for doing the same as ReferenceCollector.gd
For creating the .rst files
generate_reference: Linux/macOS script for generating the reStructuredText text files.
generate_reference.bat: Windows batch file for generating the reStructuredText text files.
Downloading the files
The github repository gds2rst_scripts has the relevant files.
With git
If you have git on your system the command
git clone https://github.com/DouglasWebster/gds2rst_scripts.git
will transfer the files to your current working directory.
Without git
If you don't have git on your system then go to the gds2rst_scripts repository and look for the green Code button, click it and click Download ZIP.

This will download a zip file containing the contents of the github repository. These can then be unzipped to your desired location.
In either case you should then have the following files in your project location
.
├── generate_reference
├── generate_reference.bat
└── godot-scripts
├── Collector.gd
├── ReferenceCollectorCLI.gd
└── ReferenceCollector.gd