docs: update notes about usage

Author: agoose77

README.md

@@ -1,3 +1,31 @@
 # MyST JS Plugin
 
-An example of deploying a MyST book that uses a JS Plugin to strike-though document prose (see `plugin.mjs`). This plugin uses `esbuild` to bundle dependencies.
+An example of a MyST JS Plugin to strike-though document prose (see `plugin.mjs`). This plugin uses `esbuild` to bundle dependencies.
+
+## Build the bundle
+
+The `esbuild` tool takes `plugin.mjs` and its dependencies as inputs, and generates a `dist/plugin.mjs` bundle. This bundle can be directly loaded by MyST without requiring a build or install step.
+
+The `build` script defined in `package.json` shows an example of using `esbuild` to generate an `mjs` module. It can be invoked by running
+
+```shell
+npm run build
+```
+
+## Using the bundled plugin
+
+The output MyST plugin can be loaded into a MyST project in several ways. The user may wish to download the plugin to their local filesystem, and write the following `myst.yml`:
+
+```yaml
+project:
+  plugins:
+    - /path/to/plugin.mjs
+```
+
+Alternatively, you can publish the built plugin to a public artifact repository, and users can directly link to it in their `myst.yml`:
+
+```yaml
+project:
+  plugins:
+    - https://www.someone-elses-myst-plugins.com/plugin.mjs
+```