Adding notes about .NET 8 limitation for MGCB

Author: SimonDarksideJ

articles/getting_to_know/howto/content_pipeline/HowTo_ExtendFontProcessor.md

@@ -6,6 +6,11 @@ requireMSLicense: true
 
 In a font description (.spritefont) file, the `<CharacterRegions>` area can be used to add additional characters to a font description. This enables you to use a [SpriteFont](xref:Microsoft.Xna.Framework.Graphics.SpriteFont) to render an additional range of characters.
 
+> [!IMPORTANT]
+> For the MGCB system (MGCB Editor), all custom pipeline extension libraries **MUST** target `.NET 8` or lower, this is due to the Editor and Command-line project only supporting `.NET 8` currently.  If you get errors with an Extension at build time, the `.NET` version of the library is the most likely cause.
+>
+> This will be resolved with the introduction of the new [Content Builder Project](/articles/getting_started/content_pipeline/content_builder_project.md) solution, which removes such limitations.
+
 For some languages, this approach is not ideal. For example, Chinese and Japanese both have many thousands of characters. Adding the full range of characters to `<CharacterRegions>` dramatically increases the size of the font asset and the time required to build the font asset. A better solution adds individual characters whenever the specific characters are needed. You can create a custom content processor to implement this solution.
 
 In this example, a file called _messages.txt_ contains all the text rendered by the game. The custom processor adds all the characters contained in the text in this file to a [FontDescription](xref:Microsoft.Xna.Framework.Content.Pipeline.Graphics.FontDescription). Then it processes the object in the standard way using the base [FontDescriptionProcessor](xref:Microsoft.Xna.Framework.Content.Pipeline.Processors.FontDescriptionProcessor) functionality. All the characters in messages.txt will then be available to the [SpriteFont](xref:Microsoft.Xna.Framework.Graphics.SpriteFont) object at run time.

articles/getting_to_know/howto/content_pipeline/HowTo_Extend_Processor.md

@@ -6,6 +6,11 @@ requireMSLicense: true
 
 MonoGame lets you modify or extend the behavior of any standard Content Pipeline processor that ships with the product. See [Standard Content Importers and Content Processors](../../whatis/content_pipeline/CP_StdImpsProcs.md) for a description of standard processors.
 
+> [!IMPORTANT]
+> For the MGCB system (MGCB Editor), all custom pipeline extension libraries **MUST** target `.NET 8` or lower, this is due to the Editor and Command-line project only supporting `.NET 8` currently.  If you get errors with an Extension at build time, the `.NET` version of the library is the most likely cause.
+>
+> This will be resolved with the introduction of the new [Content Builder Project](/articles/getting_started/content_pipeline/content_builder_project.md) solution, which removes such limitations.
+
 Because there are so many asset variants supported by different digital content creation (DCC) tools, it is often useful to be able to modify how one of the standard processors operates. The following examples illustrate some of the kinds of things you might want to do.
 
 > [!TIP]