Add package size profiling tools

[ai]

I love EmojiMart. But current library size is 110 KB (gzipped and minified). IT is too big (it is half or my app bundle size).

I want to help with size optimization. But every optimization must be started from profiling.

I added two tools:

• size-limit to prevent size regression. It will be run after test to check library size. MobX, JSS and Material UI use it too.
• webpack-bundle-analyzer to see real content of package.

This tools always showed few ways for optimization

[ai]

@EtienneLem here is current content of dist/emoji-mart.js

When you will accept this PR I will send next PR to reduce this size

[EtienneLem]

👍