Add section for Moment Timezone

[gilmoreorless]

First of all, thanks for this repo — I picked up some good tips here.

I recently wrote a plugin to reduce how much JSON data is loaded by moment-timezone, heavily inspired by moment-locales-webpack-plugin. I've added a quick section for it here, and also fixed a minor typo in the moment section.

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[gilmoreorless]

I signed it!

[googlebot]

CLAs look good, thanks!