Theme and doc updates

Author: CodyTolene

README.md

@@ -234,10 +234,10 @@ Line numbers are enabled by default, but you can turn them off like so.
 
 | Input Name               | Input Typing                         | Default Value | Description                                                                                                                                                                                                                                                                    |
 | ------------------------ | ------------------------------------ | ------------- | ------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------ |
-| **codeTheme**            | `HighlightJsTheme` (string)          | `'default'`   | The `highlight.js` code theme to use and display. Note: Only _one_ theme can be loaded on a single page at a time! The first theme to load will apply to all gists on the page.                                                                                                |
+| **codeTheme**            | `HighlightJsTheme \| undefined`      | `undefined`   | The `highlight.js` code theme to use and display. Note: Only _one_ theme can be loaded on a single page at a time! The first theme to load will apply to all gists on the page. Available themes here: https://unpkg.com/browse/highlight.js@11.6.0/styles/                    |
 | **displayOnlyFileNames** | `string \| string[] \| undefined`    | `undefined`   | Display in the DOM only the selected filename(s) from the gists files array. Can be either a string or string array. File names much match exactly, be sure to remove any leading or trailing whitespace in the provided strings.                                              |
 | **gist**                 | `NgxGist \| undefined`               | `undefined`   | Provide a static gist model here directly which will be displayed if no `gistId` is provided for remote fetching. Also this model will be displayed should a fetch fail when retrieving `gistId`, or overwritten once the pertaining `gistId` data is fetched.                 |
-| **gistId**               | `string`                             | `undefined`   | Provide the GitHub gist id to be fetched and loaded. This can be found in URL of the gists you create. For example the id `TH1515TH3G15T1D` in: https://gist.github.com/YourUserName/TH1515TH3G15T1D. Alternatively, provide a value directly in the sibling input `gist`. |
+| **gistId**               | `string`                             | `undefined`   | Provide the GitHub gist id to be fetched and loaded. This can be found in URL of the gists you create. For example the id `TH1515TH3G15T1D` in: https://gist.github.com/YourUserName/TH1515TH3G15T1D. Alternatively, provide a value directly in the sibling input `gist`.     |
 | **hideGistLink**         | `bool`                               | `false`       | Optionally hide the gist link which opens the gist on GitHub. The gist links automatically display for remote gists, but can be hidden with this feature.                                                                                                                      |
 | **materialTheme**        | `MaterialPrebuiltTheme \| undefined` | `undefined`   | Define a material core theme to apply. Ideally, you should already have your global material theme set at the root of your project so try to avoid using this if possible. Note: These are loaded from the CDN: `https://unpkg.com`                                            |
 | **showLineNumbers**      | `bool`                               | `true`        | Display or hide the line numbers in your gist code snippets.                                                                                                                                                                                                                   |

src/app/public/ngx-gist.component.ts

@@ -113,12 +113,12 @@ export class NgxGistComponent implements OnInit {
   /**
    * The `highlight.js` code theme to use and display.
    *
-   * Default: `'default'`
+   * Default: `undefined`
    *
    * Note: Only _one_ theme can be loaded on a single page at a time! The first
    * theme to load will apply to all gists on the page.
    */
-  @Input() public codeTheme: HighlightJsTheme = 'default';
+  @Input() public codeTheme?: HighlightJsTheme;
   /**
    * Define a material core theme to apply. Ideally, you should already have
    * your global material theme set at the root of your project so try to