Update the current build to use the CSS.

[billy-the-fish]

Business case - fastest solution to have the same output as the current release
Fix version -
Subject Matter Expert - Iain
Reviewer - Emily
Scope - All ditamaps in https://github.com/AgoraIO/agora_doc_source/tree/master/en-US/dita/RTC-NG. You need to:

1. Make a branch from milestone-1-update-the-dita-build.
2. In Oxygen, open /agora_doc_source/en-US/dita/RTC-NG/RTC_NG_API_Android.ditamap.
3. Choose the Agora HTML5 transformation.
   
4. Run the configuration and check the output works ok.
5. Associate the stylesheet you have made for the build to this file:
   
   Mahoosive hint, use a relative filepath so everyone can do the same thing. If the image does not help, here are the docs: https://www.oxygenxml.com/doc/versions/25.0/ug-editor/topics/webhelp-customizing-with-css.html?hl=css%2Cfile.
6. Save the project, build and check your changes.
7. Make a PR to the milestone branch and ask Iain to validate.
8. Soon as this works, do the same thing for all other ditamaps.
   Estimated -
   Acceptance criteria - HTML output has the same look and feel as the current API refs. File names do not change.
   Additional valuable information: