graphviz filter commands: add pages (#6401)

pages/common/unflatten.md

@@ -0,0 +1,17 @@
+# unflatten
+
+> Adjust directed graphs to improve the layout aspect ratio.
+> Graphviz filters: `acyclic`, `bcomps`, `comps`, `edgepaint`, `gvcolor`, `gvpack`, `mingle`, `nop`, `sccmap`, `tred`, & `unflatten`.
+> More information: <https://www.graphviz.org/pdf/unflatten.1.pdf>.
+
+- Adjust one or more directed graphs to improve the layout aspect ratio:
+
+`unflatten {{path/to/input1.gv}} {{path/to/input2.gv ...}} > {{path/to/output.gv}}`
+
+- Use `unflatten` as a preprocessor for `dot` layout to improve aspect ratio:
+
+`unflatten {{path/to/input.gv}} | dot -T {{png}} {{path/to/output.png}}`
+
+- Display help for `unflatten`:
+
+`unflatten -?`