docs: Special pages docs updates (#1341)

* docs: Update special-pages readme with style info

* docs: Update Readme with development steps

* fix: wording

special-pages/README.md

@@ -24,6 +24,19 @@ This allows each respective platform to configure their integrations to use the
     - http://127.0.0.1:3210/build/integration/pages/duckplayer
     - http://127.0.0.1:3210/build/integration/pages/special-error
 
+### Developing locally
+
+When working in this section of the repo, one tends to be focused on a certain special-page. To keep the dev cycle quick, we serve the special-pages, then only watch files in the special-page where development is happening.
+
+- `npm run serve-special-pages` run at the project root
+- `npm run watch -- --page=<page-directory-name>` run in `special-pages/` directory
+  - e.g. `npm run watch -- --page=new-tab`
+  - Follow the link from this terminal window to http://localhost:8000/ for hot loading CSS updates and more
+
+### Styles
+
+Instead of dark mode media queries in the CSS, we rely on `data-theme` attribute set at the App level and update properties inside rules for `[data-theme=dark]` or `[data-theme=dark] &`. This does change the specificity of properties set in this selector vs a media query.
+
 ### Integration Tests
 
 Ensure these commands are run from the `special-pages` folder.
@@ -36,7 +49,7 @@ npm run test-int -- --project ios
 # to *only* run screenshot tests
 npm run test.screenshots
 # to also update screenshots (if you've made changes to anything visual)
-npm run test.screenshots -- --update-snapshots 
+npm run test.screenshots -- --update-snapshots
 ```
 
 The process is as follows: