[SIM108] Support Attribute as target in assignment

[isidroas]

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[isidroas]

Doubts/TODOs:

• black

• should we use utils.to_source() instead of ast.unparse()

• isinstance(node.body[0].targets[0], (ast.Name, ast.Attribute))
  compare(node.body[0].targets[0], node.orelse[0].targets[0])

  Where compare is https://stackoverflow.com/a/66733795/16926605