Include warning about race detector compatability in plugin documentation

As described in golang#24245, the race detector isn't able to find some race conditions in plugins. This commit adds a warning about this to the plugins documentation.

Updates golang#24245

Author: ExtraE113

src/plugin/plugin.go

@@ -29,6 +29,10 @@
 //     macOS, making them unsuitable for applications intended to be
 //     portable.
 //
+//   - Plugins are poorly supported by the Go race detector. Even simple
+//     race conditions may not be automatically detected. See 
+//     [this issue](https://github.com/golang/go/issues/24245) for more information.
+//
 //   - Applications that use plugins may require careful configuration
 //     to ensure that the various parts of the program be made available
 //     in the correct location in the file system (or container image).