bui-themer: add implementation plan

Signed-off-by: Patrik Oldsberg <poldsberg@gmail.com>

plugins/bui-themer/src/components/BuiThemerPage/BuiThemerPage.tsx

@@ -14,6 +14,21 @@
  * limitations under the License.
  */
 
+/*
+
+IMPLEMENTATION PLAN:
+
+- create a utility that converts the MUI theme palette into printed CSS variables
+populating the variables in packages/ui/src/css/core.css
+- the conversion utility will be created in an adjacent `convertMuiToBuiTheme` file, which defines a `convertMuiToBuiTheme` function that accepts a MUI theme instance and returns CSS in text format
+- create tests for the conversion utility
+- Create a page that shows the generated CSS variables and allows the user to copy them
+- The page should show coverted CSS variables for all installed themes in the app, which can be acquired via the AppThemeApi, defined at packages/core-plugin-api/src/apis/definitions/AppThemeApi.ts
+- The AppThemeApi can be accessed via the useApi(appThemeApiRef) hook
+- The app themes only provide a `Provider` component that in turn provides the MUI theme. The theme can be accessed by wrapping the component in the theme's `Provider` component and then using the `useTheme` hook from MUI
+
+*/
+
 export function BuiThemerPage() {
   return <div>TODO</div>;
 }