Add the ProcessException class

Author: cedx

src/ITransformer.cs

@@ -3,7 +3,7 @@ namespace Belin.PhpMinifier;
 /// <summary>
 /// Removes comments and whitespace from a PHP script.
 /// </summary>
-public interface ITransformer: IDisposable {
+public interface ITransformer: IAsyncDisposable {
 
 	/// <summary>
 	/// Processes a PHP script.

src/ProcessException.cs

@@ -0,0 +1,16 @@
+namespace Belin.PhpMinifier;
+
+/// <summary>
+/// Exception thrown when an error has occurred during the execution of a process.
+/// </summary>
+/// <param name="fileName">The name of the document or application file that has been started.</param>
+/// <param name="message">The message that describes the error.</param>
+/// <param name="innerException">The exception that is the cause of the current exception.</param>
+public class ProcessException(string fileName, string message = "", Exception? innerException = null):
+	Exception(message.Length > 0 ? message : $"The \"{fileName}\" process could not be started.", innerException) {
+
+	/// <summary>
+	/// The name of the document or application file that has been started.
+	/// </summary>
+	public string FileName => fileName;
+}