Update package.json keywords

[keithamus]

See chaijs/chaijs.github.io#34 for more.

If you're wondering why I want you to add these keywords, here is the reasoning for each one:

• chai-plugin will let us index your plugin on the next version of the website. If you don't add this to your package.json, you wont be listed on our plugins page.
• browser will let us know that your plugin supports the browser. Please don't add this keyword if you don't support the browser. If you don't add it we'll assume the plugin does not support browsers.
• Any other keyword listed below has been listed there, because it was in our plugins.js file which is soon to be removed. If you don't want these keywords in your package.json, that's fine, but seeing as they're in our plugins.js I thought it'd be good measure to give you a chance to add them into your package.json. We'll use them to help filter our plugins page, so it is advisable to add them.

[junosuarez]

@keithamus thanks for taking the time for this PR! Package discoverability is one of the big challenges in the npm ecosystem. Anything I can do as a package author to make it easier for people to find and use the right module is a win, especially when it's as simple as merging a PR. I'm happy to help. I'll merge this and republish a new patch version.

[junosuarez]

Published as chai-interface@2.0.3

[keithamus]

Thank you very kindly @jden 😄