Fix Npm build - remove coverage folder (-60%size) - move eslint parser to devDependencies

[salvoravida]

Hi guys,
First of all, I have to say thank you for this great library!

This PR fixes two small bugs on the Npm build side:

• remove coverage folder (-60%size)
• move "@babel/eslint-parser" to devDependencies.

Regards!

[salvoravida]

fyi: https://www.unpkg.com/browse/react-grid-layout@1.3.2/coverage/

[STRML]

Thanks! These are bugs for sure so I'll do a point release to get this out ASAP and save some bytes.

[STRML]

Thanks. Published in 1.3.3. Solid fix:

Before:

npm notice package size:  245.6 kB
npm notice unpacked size: 1.2 MB

After:

npm notice package size:  131.1 kB
npm notice unpacked size: 487.7 kB

[salvoravida]

it also fixes a warning:
warning "react-grid-layout > @babel/eslint-parser@7.16.5" has unmet peer dependency "@babel/core@>=7.11.0".

great!