Update docs index

docs-src/index.md

@@ -9,19 +9,19 @@ This package is used by [Kanel](https://github.com/kristiandupont/kanel) to gene
 npm i extract-pg-schema
 ```
 
-## Usage
+## Library Usage
 
 You give it a [postgres connection config object](https://node-postgres.com/apis/client) and some options and it will connect to your database and generate
 
 ```javascript
-const { extractSchemas } = require('extract-pg-schema');
+const { extractSchemas } = require("extract-pg-schema");
 
 async function run() {
   const connection = {
-    host: 'localhost',
-    database: 'postgres',
-    user: 'postgres',
-    password: 'postgres',
+    host: "localhost",
+    database: "postgres",
+    user: "postgres",
+    password: "postgres",
   };
 
   const result = await extractSchemas(connection);
@@ -33,3 +33,28 @@ run();
 ```
 
 The generated output is a record of schemas, described with the [Schema](/api/extract-pg-schema.schema.html) type.
+
+## CLI Usage
+
+You can also use the CLI to extract the schemas from a database and write it to the console or a file in JSON format.
+
+```bash
+npx extract-pg-schema -h localhost -p 5432 -U postgres -d postgres > schemas.json
+```
+
+The CLI takes a small subset of the options that [pg_dump](https://www.postgresql.org/docs/current/app-pgdump.html) takes. You can also use the [environment variables](https://node-postgres.com/features/connecting#environment-variables) starting with `PG` to set the connection parameters.
+
+```
+Usage: extract-pg-schema [options] [DBNAME]
+
+Extract all schemas from a PostgreSQL database and print them as JSON.
+
+Options:
+    --help                      show this help
+    -h, --host=HOSTNAME         database server host or socket directory
+    -p, --port=PORT             database server port
+    -U, --username=USERNAME     database user name
+    -d, --dbname=DBNAME         database name to connect to
+    -n, --schema=SCHEMA         include schema regular expression (may be given multiple times)
+    -N, --exclude-schema=SCHEMA exclude schema regular expression (may be given multiple times)
+```