Update Readme file for magento2 repository

[sidolov]

Description

Updated readme.md

• Added Maintainers section
• Added Contributors section
• Changed links to documentation

Fixed Issues (if relevant)

none

Manual testing scenarios

none

Contribution checklist

• Pull request has a meaningful description of its purpose
• All commits are accompanied by meaningful commit messages
• All new or changed code is covered with unit/integration tests (if applicable)
• All automated tests passed successfully (all builds on Travis CI are green)

[magento-engcom-team]

Hi @okorshenko, thank you for the review.
ENGCOM-1353 has been created to process this Pull Request

[okorshenko]

@magento-engcom-team give me 2.2.3 verification instance

[magento-engcom-team]

Hi @okorshenko. Thank you for your request. I'm working on Magento 2.2.3 instance for you

[magento-engcom-team]

Hi @okorshenko, here is your Magento instance.
Admin access: http://i-14791.engcom.dev.magento.com/admin
Login: admin Password: 123123q
Instance will be terminated in up to 3 hours.

[magento-engcom-team]

Hi @sidolov. Thank you for your contribution.
Changes from your Pull Request will be available with the upcoming 2.1.15 release.