Redux devtools are being included in production builds

[samhh]

Adding ~100kb via Lodash I think. Not a big deal for a local WebExtension, but still..

Experiment with: webpack -p --stats --json > webpack-build-stats.json (there'll be 4 bad lines at the top of this output file that will need removing) and Webpack Visualizer

[samhh]

yarn build && ls -l dist/content

Some measurements:

Commit or change	Size (approx/rounded)	Notes
https://github.com/SamHH/bukubrow/commit/4236a81a8e306ec96554c98854ec19de6ffb49bb	402kB
https://github.com/SamHH/bukubrow/commit/f1e05234e252eb370dd7b596fe2602b7c4beab7d	402kB	No change.
Remove remote-redux-devtools	284kB
tsconfig.json: module to esnext	402kb	No change.
tsconfig.json: module and target to esnext	400kB