dune: add page (#6674)

pages/common/dune.md

@@ -0,0 +1,20 @@
+# dune
+
+> A build system for OCaml programs.
+> More information: <https://dune.build>.
+
+- Build all targets:
+
+`dune build`
+
+- Clean up the workspace:
+
+`dune clean`
+
+- Run all tests:
+
+`dune runtest`
+
+- Start the utop REPL with compiled modules automatically loaded into it, to remove the need to load them by hand:
+
+`dune utop`