Not using struct tags

Nobody has claimed this yet.

First, I would like to thank you for the library!.

From an user's perspective, we have been really successful in creating an internal Kafka implementation using `goavro`!.

Within the team, especially on me, there was a question that has been bothering my mind, that is:

What was the rationale behind not using Struct tags vs maps?. (speed? avoid reflection?)

I've seen that you even state on the README.md the following remark:

> Goavro does not use Go's structure tags to translate data between native Go types and Avro encoded data.

I think that means that you had that approach in mind while creating the library.

Start with the struct-tags statement in README.md and inspect the library's documented handling of native Go types, maps, and Avro encoding. Clarify the rationale for not using Go struct tags, including any relevant trade-offs, and update the documentation if the project agrees on wording.

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