docs: Add new options to ember-app readme.

Documents `broccoliConcat` and `appClasses`.

Author: Tim Lindvall

packages/@css-blocks/ember-app/README.md

@@ -29,6 +29,8 @@ The following options can be passed as options to the `css-blocks` property in y
 * `analysisOpts` - Template analysis options. You probably don't need to set these.
 * `parserOpts` - Options passed to the CSS Blocks parser and compiler. If not set, these options are loaded automatically from a `css-blocks.config.js` file. Using a CSS Blocks configuration file will allow other tools like the CSS Blocks command line (`@css-blocks/cli`) to load the same options as your ember application.
 * `optimization` - Options passed to the Opticss optimizer. This can be used to selectively enable or disable specific optimizations or to explicitly disable all optimizations by setting the `enable` option to `false`.
+* `broccoliConcat` - Options that control the behavior of broccoli-concat, which is used to concatenate CSS files together by ember-app during postprocess. If this is set to false, broccoli-concat will *not* run and you'll need to add additional processing to add the CSS Blocks compiled content to your final CSS build artifact.
+* `appClasses` - List of classes that are used by application CSS and might conflict with the optimizer. You should add any short class names (~5 characters) to this list so the optimizer doesn't use these when building the CSS Blocks compiled output. This is a convenience alias for `optimization.rewriteIdents.omitIdents.class[]`. It has no effect if optimization is disabled.
 
 ## Common Gotchas