Keep up to date

[hienvd]

Update changes to keep the repo up to date with the original repository

[timnqp]

The part 6.SOLID is recently added.
Can I take up part 6 @hienvd ?

[hienvd]

Of course @quangphuc789

[timnqp]

There is a difference in Classes & SOLID. I will take care of this. @hienvd

[phamvanhan68]

There are a few changes since 2017. Could you guys keep it up to date, please? @hienvd @timnqp

[timnqp]

@phamvanhan68 Definitely! Will do it this week!