emacsclient: add page (#1845)

pages/common/emacsclient.md

@@ -0,0 +1,15 @@
+# emacsclient
+
+> Open files in an existing emacs server.
+
+- Open files in an existing Emacs server (using GUI if available):
+
+`emacsclient {{filename}}`
+
+- Open file in console mode (without X window):
+
+`emacsclient -nw {{filename}}`
+
+- Open a file in an existing emacs frame and return immediately:
+
+`emacsclient -n {{filename}}`