I'm planning to write a html5 app (not a webapp) for Ubuntu Touch using Ubuntu-SDK. Is it possible to use the bottom edge navigation in case of html apps?
Although there's nothing to stop you rolling your own bottom edge navigation in an HTML5 app :-) You could even possibly propose such a feature to the HTML5 sdk if you have success implementing it.
At the moment there is no such functionality provided by the Ubuntu HTML5 sdk. See https://developer.ubuntu.com/api/apps/html5/current/UbuntuUI/ for a complete list of provided components.
Although there's nothing to stop you rolling your own bottom edge navigation in an HTML5 app :-) You could even possibly propose such a feature to the HTML5 sdk if you have success implementing it.