With the recent update, some things have changed, including the spellchecker. There is no designated spell check button anymore but instead moodle will spell check for you automatically. As you can see below, it picked up the typo and underlined the word for me. After I clicked CTRL + right click (On a mac I pressed and held down the CTRL button and while keeping it pressed down I right clicked my mouse) the second option appeared. That allowed me to choose form one of the suggestions and possibly add the word to my dictionary.
Image 1: Moodle identifies incorrectly spelled words for me automatically.