PR Summary

Fixes #806 and #904
It is well know that PowerShell's += operator always creates a new array under the hood even if the array type is not of fixed size.
Because SSA (single statement analysis) is not fully implemented at the moment, the detection for the object type can not catch all cases. For example it does not work inside function definitions or cannot determine if the object is of type string at the moment or cases like $a=@(); $a+=$foo.
The rule documentation includes all possible info even if strings cannot be caught at the moment.

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