Add badge to display install size

[styfle]

This adds a badge to the README.md file to display the npm install size

[coveralls]

Coverage remained the same at 84.224% when pulling dec45ba on styfle:patch-1 into df41bdb on TypeStrong:master.

[blakeembrey]

This doesn't appear relevant and the website is down. If you can state the value of the addition and get the badge hosted alongside the rest (instead of on a down domain), I'll reconsider the PR.

[styfle]

Hi @blakeembrey

Sorry for the inconvenience, Package Phobia is getting a lot of traffic now and went down.

The value is to show that ts-node is not a huge implementation of node.js but rather a 2 MB middleman.

These are metrics that are not easily attainable so the badge is nice to show new users who are interested in the project as well as devs can try to achieve a smaller size.

Package Phobia actually caught a bug in TypeScript 5 days ago where the publish size doubled microsoft/TypeScript#23339 (comment)

[blakeembrey]

Cool, thanks. That seems reasonable and I'd love to accept it, do you think it could be added to https://shields.io/?

[styfle]

Thanks! 🎉
I'll need to figure out how to add it to shields.io
I guess I should just make a PR so that shields.io/packagephobia is proxy to my server?

[blakeembrey]

I noticed bundlephobia is already on there, it seems like you could use that for reference? I've never really looked into it myself.

Reference: badges/shields#1481