Fixed formatting.

lib/elements/custom-style.html

@@ -22,17 +22,18 @@
    * advantage of [shady DOM](https://github.com/webcomponents/shadycss) shims
    * for style encapsulation, custom properties, and custom mixins.
    *
-   * - Document styles defined in a custom-style are shimmed to ensure they
+   * - Document styles defined in a `<custom-style>` are shimmed to ensure they
    *   do not leak into local DOM when running on browsers without native
    *   Shadow DOM.
-   * - Custom properties can be defined in an custom-style. Use the `html` selector 
+   * - Custom properties can be defined in a `<custom-style>`. Use the `html` selector 
    *   to define custom properties that apply to all custom elements.
-   * - Custom mixins can be defined in a custom-style, if you import the optional 
-   *   [apply shim](https://github.com/webcomponents/shadycss#about-applyshim)(`shadycss/apply-shim.html`).
+   * - Custom mixins can be defined in a `<custom-style>`, if you import the optional 
+   *   [apply shim](https://github.com/webcomponents/shadycss#about-applyshim)
+   *   (`shadycss/apply-shim.html`).
    *
    * To use:
    * 
-   * - Import the custom-style element.
+   * - Import `custom-style.html`.
    * - Place a `<custom-style>` element in the main document, wrapping an inline `<style>` tag that
    *   contains the CSS rules you want to shim.
    *