[improvement] readvalue is restricted to only primitive or a list of primitive types

[piggybankwang]

Hi
we realize this function https://github.com/mercari/hcledit/blob/main/internal/converter/converter.go can only return primitive and list of primitive types
we'd like to help contribute to read values like map of map, list of map
so we can handle READ more complex field

i.e.

if ctyVal.IsNull() {
		return nil, nil
	} else if ctyVal.IsMapType() || ctyVal.IsObjectType() {
		return GetAttributeMapValues(ctyVal)
	} else if ctyVal.IsListType() || ctyVal.IsTupleType() {
		return GetAttributeSliceValues(ctyVal.AsValueSlice())
	} else if ctyVal.IsSetType() {
		return GetAttributeSliceValues(ctyVal.AsValueSet().Values())
	} else if ctyVal.IsPrimitiveType() {
		switch ctyVal {
		case cty.Bool:
			return ctyVal.True() == true, nil
		case cty.String:
			return ctyVal.AsString(), nil
		case cty.Number:
			return GetAttributeNumValue(ctyVal), nil
		}
	}