please add alt hotkey as well, Ctrl and shift are used for other tasks

Edit:
Thanks!
Alt however conflicts with the menu bar toggle, here's how to disable it:
Go to 'about:config?filter=ui.key.menuAccessKeyFocuses' website and search for 'ui.key.menuAccessKeyFocuses'. Disable it and it and problem is solved.
It would be awesome if the extention overwrote this firefox function automatically.
Thanks again for listening to the feedbacks!

選択したテキストを、右クリックメニューから英辞郎で検索することもできる。Quantum になってから探してたけどようやく見つけれた。