Add .gitignore

.gitignore

@@ -0,0 +1,22 @@
+# build output
+out/
+target/
+*.class
+
+# JFR recordings produced by the demos (they are regenerated on every run)
+*.jfr
+
+# raw unified GC logs -- large, machine-specific, regenerated by scripts/run-all
+logs/
+
+# local run bookkeeping
+run-all-transcript.txt
+run-all-errors.txt
+
+# editors
+.idea/
+*.iml
+.vscode/
+.DS_Store
+
+# results/ IS committed on purpose -- it is the evidence for the blog post