added ar.md

pages/common/ar.md

@@ -0,0 +1,11 @@
+#ar
+
+> Create, modify, and extract from archives (.a .so .o)
+
+- Extract members of the archive
+
+`ar -x libfoo.a`
+
+- List the content (files) of libfoo.a
+
+`ar -t libfoo.a`