[NSE-330]Refine Readme introduction

[HongW2019]

What changes were proposed in this pull request?

made small modification of Readme introduction for better user experience.

How was this patch tested?

N/A

[github-actions]

#330

[HongW2019]

@zhouyuan Hi Yuan, we have tried to modify the Introduction for better user experience. Please take a review and help point out more modifications needed to provide user a concise and comprehensive introduction to Native SQL Engine. Thanks a lot!

[zhouyuan]

@zhouyuan Hi Yuan, we have tried to modify the Introduction for better user experience. Please take a review and help point out more modifications needed to provide user a concise and comprehensive introduction to Native SQL Engine. Thanks a lot!

@HongW2019 thanks for starting this work, to me the most important part is the get-started(https://github.com/oap-project/native-sql-engine#get-started). This section needs more clean up, especially from the perspective of an un-familiar user
@weiting-chen may also have some inputs