Add a hint that developer can automatically generate Grpc proto interface by a third package

[yar2001]

Add a hint that developer can automatically generate proto interface by a third package, which will help me a lot if I had read it at the first time.

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What kind of change does this PR introduce?

• Bugfix
• Feature
• Code style update (formatting, local variables)
• Refactoring (no functional changes, no api changes)
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What is the current behavior?

Issue Number: N/A

What is the new behavior?

Does this PR introduce a breaking change?

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Other information

[kamilmysliwiec]

LGTM