gc: add page (#18537)

Co-authored-by: Managor <42655600+Managor@users.noreply.github.com>

pages/common/gc.md

@@ -0,0 +1,24 @@
+# gc
+
+> Count nodes, edges, connected components, or clusters in Graphviz `.dot` files.
+> More information: <https://graphviz.org/pdf/gc.1.pdf>.
+
+- Count nodes and edges in a file:
+
+`gc {{path/to/file.dot}}`
+
+- Count only [n]odes:
+
+`gc -n {{path/to/file.dot}}`
+
+- Count only [e]dges:
+
+`gc -e {{path/to/file.dot}}`
+
+- Count [c]onnected components:
+
+`gc -c {{path/to/file.dot}}`
+
+- Display help:
+
+`gc -?`