add tasty integration notes

docs/tasty-integration.md

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+# Using ghciwatch with tasty
+
+Tips and tricks for using ghciwatch with the [Tasty][tasty] test framework.
+
+[tasty]: https://hackage.haskell.org/package/tasty
+
+Ghciwatch will wait for GHCi to print output, and it can end up waiting forever
+if the Tasty output is buffered. Something like this works:
+
+```haskell
+module TestMain where
+
+import Control.Exception (bracket)
+import System.IO (hGetBuffering, hSetBuffering, stdout)
+import Test.Tasty (TestTree, defaultMain, testGroup)
+
+-- | Run an `IO` action, restoring `stdout`\'s buffering mode after the action
+-- completes or errors.
+protectStdoutBuffering :: IO a -> IO a
+protectStdoutBuffering action =
+  bracket
+    (hGetBuffering stdout)
+    (\bufferMode -> hSetBuffering stdout bufferMode)
+    (const action)
+
+main :: IO ()
+main = protectStdoutBuffering $ defaultMain $ mytestgroup
+```
+
+## `tasty-discover` issues
+
+If you add a new test file, you may need to write the top level
+[`tasty-discover`][tasty-discover] module to convince ghciwatch to reload it.
+[`tasty-autocollect`][tasty-autocollect] relies on a compiler plugin and seems
+to avoid this problem.
+
+[tasty-discover]: https://hackage.haskell.org/package/tasty
+[tasty-autocollect]: https://github.com/MercuryTechnologies/ghciwatch/pull/321/files?short_path=c86caa3#diff-c86caa33ad4639b624ef8db59e739295f362bf4c211bed24c8ba484c79af9bdb