C#: Add change note for compression extractor option.

Author: michaelnebel

csharp/ql/src/change-notes/2022-02-23-extractor-option-compression.md

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+---
+category: minorAnalysis
+---
+* The C# extractor now accepts an extractor option `compression`, which is used to decide the compression format for TRAP files. The legal options are `brotli` (default), `gzip` or `none`.
+* The C# extractor no longer accepts `--no-brotli` or `--brotli` flags to switch between `gzip` and `brotli` as compression method for TRAP files.