Message interface type definitions should copy the class JSDoc

[jdforsythe]

protobuf.js version: 6.8.8

When generating Typescript definitions for .proto files, the JSDoc comment is copied correctly to the resulting class in the type defs, but the interface for that class just has a comment reading: "Properties of a [classname]". This isn't a useful comment and it makes more sense for the consumer of the types to make the interface doc a duplicate of the class doc.

syntax = "proto3";

package example;

import "google/protobuf/empty.proto";

/**
 * Service to demonstrate the example
 *
 * Some further description
 */
service ExampleService {

  /**
   * Get a message telling you hello
   */
  rpc sayHello (Empty) returns (HelloMessage) {}
}

/**
 * Message response from the sayHello endpoint
 *
 * Contains a friendly message
 */
message HelloMessage {
  /**
   * A friendly message
   */
  string message = 1;
}

pbjs -t static-module -w commonjs --es6 -o lib/index.js proto/*.proto
pbts -o lib/index.d.ts lib/index.js

/// ...

/** Properties of a HelloMessage. */
interface IHelloMessage {

    /** A friendly message */
    message?: (string|null);
}

/**
 * Message response from the sayHello endpoint
 *
 * Contains a friendly message
 */
class HelloMessage implements IHelloMessage { /* ... */ }

As you can see, the comments for the properties of the interface are copied but the comment for the interface itself is just "Properties of a ClassName", where it would be more useful to have copied the comment from the class.