Update NU1105.md to contain invalid tfm (#3418)

Author: Nigusu-Allehu

docs/reference/errors-and-warnings/NU1105.md

@@ -12,6 +12,8 @@ f1_keywords:
 
 # NuGet Error NU1105
 
+## Scenario 1
+
 > Unable to read project information for 'ProjectFile'. The project file may be invalid or missing targets required for restore.
 
 ### Issue
@@ -36,3 +38,16 @@ The error could also mean that the project is unloaded.
 * If you are using Visual Studio 2019 or later, NuGet has the ability to re-use artifacts from the previous restore for unloaded projects. In order for this scenario to work, you need to ensure that all projects currently in the solution have been restored from the command line prior to loading them in Visual Studio.
 
 * Alternatively, reload the project.
+
+## Scenario 2
+
+> Invalid target framework 'net.6.0'
+
+### Issue
+The project file exists but specifies an invalid target framework: `'net.6.0'`.
+This can occur due to a typo or use of an unsupported format.
+
+### Solution
+
+Update the project file to use a valid target framework. In this case, replace `'net.6.0'` with `'net6.0'` (without the extra dot).
+For a full list of supported frameworks and their correct formats, refer to the [.NET Target Frameworks](/dotnet/standard/frameworks) documentation.