README.md: add more information

Add a screenshot of the documentation website and more information
about the Python/Node.js setup and usage.

README.md

@@ -1,9 +1,46 @@
 # ISEAL Core Metadata Set
 The ISEAL Core Metadata Set (ISEAL Core) is a set of structured terms and vocabularies that can be used as metadata to describe, share, and reuse different digital resources across the [ISEAL Community](https://www.isealalliance.org/) and broader set of stakeholders. The resources described using the ISEAL Core are those that sustainability systems typically collect, curate, manage, use, publish and archive. They may be datasets, published research, certificates, videos, images, maps, or other organizational documentation.
 
+<p align="center">
+  <img width="600" alt="Screenshot of ISEAL Core Metadata Set documentation" src="screenshot.png">
+</p>
+
+You can see a user-friendly version of the schema [here](https://alanorth.github.io/iseal-schema/).
+
+## Requirements
+
+- Python 3.7+ (for parsing the schema)
+- Node.js 12+ (for generating the HTML documentation site)
+
+## Python Setup
+Create a Python 3 (3.7+) virtual environment and install the requirements:
+
+```console
+$ python3 -m venv virtualenv
+$ source virtualenv/bin/activate
+$ pip install -r requirements.txt
+```
+
+Then run the utility scripts to parse the schema:
+
+```console
+$ ./util/generate-hugo-content.py -i ./idss_schema_fields_new2.xlsx --clean -d
+```
+
+## Node.js Setup
+To generate the HTML documentation site:
+
+```console
+$ cd site
+$ npm install
+$ npm run build
+```
+
 ## TODO
 
 - Update links to final version (from alanorth to iseal GitHub)
+- Extract controlled vocabularies and schema.csv to data directory, remove openpyxl dependency
+- Add more information and instructions to README.md
 
 ## License