Document process stdio handling

Add inline comments in GenerateCsWinRTStubExes.cs to clarify handling of stdout/stderr and the sequence of starting asynchronous reads (BeginOutputReadLine/BeginErrorReadLine) before waiting for process exit. Improves code readability by documenting intent around receiving stdio lines and blocking until completion.

Author: Sergio0694

src/WinRT.Generator.Tasks/GenerateCsWinRTStubExes.cs

@@ -695,6 +695,7 @@ private bool InvokeCompiler(string arguments, string workingDirectory, string st
             StringBuilder stdoutBuilder = new();
             StringBuilder stderrBuilder = new();
 
+            // Handle receiving stdio lines
             process.OutputDataReceived += (_, e) =>
             {
                 if (e.Data is not null)
@@ -703,6 +704,7 @@ private bool InvokeCompiler(string arguments, string workingDirectory, string st
                 }
             };
 
+            // Handle receiving stderr lines
             process.ErrorDataReceived += (_, e) =>
             {
                 if (e.Data is not null)
@@ -711,6 +713,7 @@ private bool InvokeCompiler(string arguments, string workingDirectory, string st
                 }
             };
 
+            // Start reading asynchronously and then block until the process completes
             process.BeginOutputReadLine();
             process.BeginErrorReadLine();
             process.WaitForExit();