polybar, polybar-msg: add page (#10446)

pages/common/polybar.md

@@ -0,0 +1,16 @@
+# polybar
+
+> A fast and easy-to-use status bar.
+> More information: <https://github.com/polybar/polybar/wiki>.
+
+- Start Polybar (the bar name is optional if only one bar is defined in the config):
+
+`polybar {{bar_name}}`
+
+- Start Polybar with the specified config:
+
+`polybar --config={{path/to/config.ini}} {{bar_name}}`
+
+- Start Polybar and reload the bar when the config file is modified:
+
+`polybar --reload {{bar_name}}`