Use inline comment if no other comment is available

[evilnoxx]

I needed to generate jsonschema to document some code generated using protoc.

The protobuf files were already documented like so:

message Event {
    string id = 1;  // the id of the event
    string name = 2; // name of the event
}

And protoc generates a struct like so:

type RuleEvent struct {
	state         protoimpl.MessageState
	sizeCache     protoimpl.SizeCache
	unknownFields protoimpl.UnknownFields

	Id   string `protobuf:"bytes,1,opt,name=id,proto3" json:"id,omitempty"`     // the id of the event
	Name string `protobuf:"bytes,5,opt,name=name,proto3" json:"name,omitempty"` // name of the event
}

The purpose of this pull request is to use the inline comments if the field comment is not available.
If the field comment is available, then the inline comment is still ignored.

[samlown]

Thanks for this! Looks great!