Refacted so that the toggleNativeAppSelectionMode script (NVDA+shift+f10) is defined on the base BrowseModeDocumentTreeInterceptor, and so cursorManager's copyToClipboard script honors native selection mode, passing through to the application if turned on, no longer unnecessarily overriding the script at a higher level. Toggling native selection mode is only available in Firefox, anywhere else providing a message that it is unsupported.
If one wants to test native selection mode in Chromum, they can:
* Focus a document in a Chromium browser.
* Ensure you are in browse mode.
* Open the NvDA Python console
* Type `nav.treeInterceptor._nativeAppSelectionModeSupported=True` and press enter.
* Close the Python console, and now the toggle native selection mode script will work.