[BUG] Implement avro schema data type

[akkshitgupta]

Currently, the Avro Schema Input Processor does not handle the map, fixed and byte datatypes. This issue is a continuation of the work done in pull request #1753

Now, we need to add/implement:

• Dictionary Model for map data type as suggested in feat: add Avro Schema input processor #1753 (comment) conversation
• String Model for fixed and byte data type: need to update the toStringModel function in https://github.com/asyncapi/modelina/pull/1753/files#diff-7172970fb3505bd86705eca0c2ef14740d102e6f4e828f18bedc431ba2097241
• unit tests for the added data types
• changes in docs/usage.md covering edge cases and other related things.
• a work-around to differentiate Avro Schema from JSON Schema - feat: add Avro Schema input processor #1753 (comment)

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