Feature/#111 modernize upgr deps

[StarpTech]

1. Upgrade to latest sharp version to support Node.js 12
2. Use prettier and standardjs
3. Use husky to run pre-commit hook
4. Use Async / Await, const/let
5. Use Node.js 8 as minimum version because support for node 6 is over!
6. FIX - Wrong file count when using multiple formats.
7. FIX - Emit multiple files when using multiple formats.
8. FIX - Includes Avoid renaming extname in case of jpg or jpe #116
9. FIX - Includes https://github.com/mahnunchik/gulp-responsive/pull/110/files

[krisdante]

I do not confirm that the jpeg -> jpg problem is solved. Actually I haven't got it before and now I have it. #136

[abelardolg]

Hi there,

I have a problem with it and I couldn't fix it. I don't know how to solve it.

2021-04-07T11_42_32_517Z-debug.log

Ubuntu 20.10
node 12.8.2
npm: 6.14.8

Best regards.