misc: prefix ValidationTask with I, it's an interface

Mention in PR comment script that you now need to be logged into GitHub to download artifacts.

src/Ryujinx.BuildValidationTasks/IValidationTask.cs

@@ -0,0 +1,7 @@
+namespace Ryujinx.BuildValidationTasks
+{
+    public interface IValidationTask
+    {
+        public bool Execute(string projectPath, bool isGitRunner);
+    }
+}