docs(guides): fix missing text in author-libraries (#1842)

This fixes #1832 with the suggested text from that issue.

Author: davidjb

src/content/guides/author-libraries.md

@@ -307,7 +307,7 @@ Or, to add as standard module as per [this guide](https://github.com/dherman/def
 
 The key `main` refers to the [standard from `package.json`](https://docs.npmjs.com/files/package.json#main), and `module` to [a](https://github.com/dherman/defense-of-dot-js/blob/master/proposal.md) [proposal](https://github.com/rollup/rollup/wiki/pkg.module) to allow the JavaScript ecosystem upgrade to use ES2015 modules without breaking backwards compatibility.
 
-W> The `module` property should point to a script that utilizes ES2015 module syntax but no other syntax features that aren't yet supported by browsers or node. This enables
+W> The `module` property should point to a script that utilizes ES2015 module syntax but no other syntax features that aren't yet supported by browsers or node. This enables webpack to parse the module syntax itself, allowing for lighter bundles via [tree shaking](https://webpack.js.org/guides/tree-shaking/) if users are only consuming certain parts of the library.
 
 Now you can [publish it as an npm package](https://docs.npmjs.com/getting-started/publishing-npm-packages) and find it at [unpkg.com](https://unpkg.com/#/) to distribute it to your users.