Document DAG script in README

README.md

@@ -3,3 +3,28 @@
 This is the source repository for the Zcash Developers Hub website: https://zcash.github.io/developers/
 
 For now, this repo hosts the script used to generate ECC's development dependency graph, and a workflow that generates and hosts it.
+
+## Generating DAGs
+
+The `zcash-issue-dag.py` script has two required environment variables:
+
+- `GITHUB_TOKEN`: a GitHub API token with permission to read the necessary repositories.
+- `ZENHUB_TOKEN`: a ZenHub API token.
+
+It also supports several configuration options, also supplied as environment variables:
+
+- `DAG_VIEW=[core|wallet|zf]`: The DAG to render (default: `core`).
+- `SHOW_MILESTONES=[true|false]`: Whether or not to render GitHub milestones as boxes (default: `false`).
+- `INCLUDE_FINISHED=[true|false]`: Whether or not to include closed issues with no open blockers (default: `false`).
+
+Here's an example script for easily running the DAG script:
+
+```bash
+#!/usr/bin/env bash
+DAG_VIEW=core \
+SHOW_MILESTONES=false \
+GITHUB_TOKEN=<INSERT> \
+ZENHUB_TOKEN=<INSERT> \
+python ./zcash-issue-dag.py
+```
+