Rule request: Avoid using the Assignment by Addition Operator (`+=`) to build a string

Summary of the new feature

Strings are immutable. Each addition to the string actually creates a new string big enough to hold the contents of both the left and right operands, then copies the elements of both operands into the new string. For small strings, this overhead may not matter. For large strings, this can affect performance and memory consumption.
This will create more awareness of the possible performance impact of using the Assignment by Addition Operator (+= ), see also:

• Avoid the increase assignment operator (+=) for building strings
• PowerShell scripting performance considerations / String addition

Proposed technical implementation details (optional)

See (PowerShell based) prototype AvoidPlusEqualsToBuildStrings at: https://github.com/iRon7/PSRules

What is the latest version of PSScriptAnalyzer at the point of writing

1.21.0

Beginne mit der Durchsicht des verknüpften Prototyps AvoidPlusEqualsToBuildStrings und der Referenzen des Issues zur Addition von PowerShell-Zeichenfolgen. Untersuche anschließend die vorhandenen Regelmuster und Tests von PSScriptAnalyzer. Die Aufgabe ist erfüllt, wenn eine Regel die Verwendung von += zum Erstellen von Zeichenfolgen erkennt und sie konsistent gemäß den Analyzer-Konventionen des Projekts meldet.