e2e Testing: Add README for editor action bar (#6168)

Added README for editor-action-bar tests to log manual tests that can't be automated.

test/e2e/tests/editor-action-bar/README.md

@@ -0,0 +1,9 @@
+# Editor Action Bar Testing
+This group of tests cover the use of the action bar feature on the editor tab(s)
+
+## Manual Tests
+- Verify HTML file can be opened directly in a browser from action bar button. See [Issue 6047](https://github.com/posit-dev/positron/issues/6047)
+  - Open HTML file, then click "Open in Browser" button on action bar. Verify it opens.
+  - _This can't be automated as it opens a browser window._
+
+## Additional Setup Notes