[proposal] proposal doc of Network QoS

[zwzhang0107]

What is your proposal:

Why is this needed:

Is there a suggested solution, if so, please add it:

[zwzhang0107]

/area koordlet

[zwzhang0107]

/assign @lucming

[koordinator-bot[bot]]

@zwzhang0107: GitHub didn't allow me to assign the following users: lucming.

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In response to this:

/assign @lucming

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