Add a README for using the SB Ozone prototype

b/371272304

ui/ozone/platform/starboard/README.md

@@ -0,0 +1,16 @@
+TODO(cobalt): Remove the below section. Don't merge this into main without cleaning it up.
+
+For the experimental/ozone branch:
+
+How to run:
+ * `git checkout origin/experimental/ozone`
+   * If the above command can't find the branch, you may need to git pull or sync gclient: `gclient sync --no-history --force -r $(git rev-parse @)`
+ * `python cobalt/build/gn.py -p linux-x64x11 -c qa`
+ * `autoninja -C out/linux-x64x11_qa cobalt`
+ * `out/linux-x64x11_qa/cobalt`
+
+Known Issues:
+ * Cobalt window and content area sizes don't match. The window will be far larger than the displayed content. (Being worked on by Tyler).
+ * Passing focus to the content area is finicky. The easiest way I've found to do it is to click the back button on the navigation bar.
+ * Not all keyboard inputs work. Input mapping is still in progress. (Being worked on by Madhura).
+ * There is a navigation bar and the webapp isn't full screen within the content area. This is intentional for now to make other things easier, but can be removed with the flag `--content-shell-hide-toolbar` (though there will still be a border).