This is a simple addon that I wrote years ago. It allows one to simply highlight and open a tab that queries TheFreeDictionary.com for quick word lookups. TheFreeDictionary.com is free, fast and noticeably absent of annoying ads, unlike many others.
I wanted to update it to the latest web extensions standard to support multiple browsers and move away from the Mozilla LUA-based extensions of yore. I also wanted to use the latest Javascript features and some build automation.
npm install
npm run dev
Chrome allows loading unpacked extensions (the output of the dev build script above) by navigating to chrome://extensions/ and clicking Load unpacked extension.
Similarly, Mozilla Firefox (Quantum) allows one to install unpacked extensions by navigating to about:addons and clicking the gear icon and clicking Install... and then Debug....
npm run build
If you choose to fork this project as a base, consider that it is currently setup to not utilize web-ext to publish directly to Mozilla (web-ext is a Mozilla utility and would not publish to Chrome anyway). The current assumption is that the extension is manually uploaded to the Chrome or Mozilla web stores.