Easymotion: expand navigation keys

One thing I never really understood was the rationale behind the keys setting on line 7. The comment says it only uses the left home row, which isn't the case: J, K, O, and N are all on the right. Some home row keys, like L, aren't included, while other non-home row keys are like E and N. So, I'm not quite sure why this subset of keys are faster to type than say all the letters and basic punctuation (semicolon, comma, period), which are at-most distance 1 from home row.

Instead, use letters + semicolon as navigation keys, since they are all easily
accessible (easymotion default).