Use same options in proto compile and load

[paskozdilar]

First of all, thank you for this example repository! I've been using it as a reference countless times while writing TypeScript services.

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I've noticed a small footgun in proto-loader example:

When using the flags --oneofs for the build:proto step, the generated code provides a virtual property for each oneof message type.
However, if the same option is not used in loadSync method, the virtual property is always undefined.

I've added the options to match those used in the build:proto, so people in the future will avoid the same mistake.

[badsyntax]

Wasn't aware of this, thank you!