Update release notes

release-notes/8-x.md

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 # Release Notes for PROSE SDK versions 8.x
+## [Release 8.20.0](https://www.nuget.org/packages/Microsoft.ProgramSynthesis/8.20.0) - 2023/03/31
+- Transformation.Formula
+  - Added learning of arithmetic constants.
+  - Added support for mixed number types (int, double, decimal) in the same column. Translations are now number type agnostic for all target languages.
+  - Added number formatting for the result of a constant arithmetic operation.
+  - Added default columns priority based on data availability for each column.
+  - Added suppression for formulas referencing columns with incomplete data.
+  - Added FromNumberStr operator to select an input number as a string.  Used only in Excel.Added number formatting for the result of a constant arithmetic operation.
+- Extraction.Json
+  - BREAKING CHANGE: Constraint Auto renamed to AutoFlatten. NOTE: This will also break any serialized Extraction.Json programs.
+- Transformation.Table and Split.Text
+  - Added a ForbiddenColumnNames property to PowerQueryTranslationConstraint
+  - Add option to remove the original column for a split operation
+  - Added OutputColumnNames as a metadata in the translation result
+- Data.Magic and Common.OpenAI
+  - Rename namespace beginning with Microsoft.PROSE to Microsoft.ProgramSynthesis for consistency with other projects
+- Common
+  - Added Metadata property in ITable; as well as a ITableMetadata interface for specifying metadata about the table.
+  - Removed the NumPrefixRows property (breaking change); refactored this property to be an ITableMetadata instead.
+- Detection
+  - Added new method FilterTypeIdentifier.GetFileTypeInfo which returns an object containing information about a file and may be passed to new overloads of AddInput on Extraction.Json.Session and Read.FlatFile.Session to enable learning programs to parse the identified file.
+  - Encoding detection now better handles partially corrupted ascii files but also has an option for previous behavior.
 
 
 ## [Release 8.19.0](https://www.nuget.org/packages/Microsoft.ProgramSynthesis/8.19.0) - 2023/02/27