is there any browser plugin (doesn't matter which browser) that can give you a list of word suggestions as you type inside a textarea (e.g. like this one on superuser, or email content area).
For example, you start typing a letter 'a', it pop-ups a list of words starting with 'a', ordered by how frequent you use those words.
Think about those typing aids on smart phones, but this one is for PC browsers.
Best if the list of word suggestions is customizable (i.e. you can add/remove/edit the words)