xmobar: add module (#2120)

* xmobar: Add module

* xmobar: Add test case

xmobar: Add test default.nix

* xmobar: Order lists alphabetically

* xmobar: Change colon to comma in description

* xmobar: Fix macos tests

* xmobar: Remove extra line

* xmobar: Add literalExample

Co-authored-by: Sumner Evans <me@sumnerevans.com>

* xmobar: Update extraConfig description

Co-authored-by: Sumner Evans <me@sumnerevans.com>

tests/modules/programs/xmobar/basic-configuration.expected

@@ -0,0 +1,19 @@
+Config
+  { font        = "Fira Code"
+  , borderColor = "#d0d0d0"
+  , border      = FullB
+  , borderWidth = 3
+  , bgColor     = "#222"
+  , fgColor     = "grey"
+  , position    = TopSize C 99 30
+  , commands    =
+      [ Run Cpu ["-t", "cpu: <fc=#4eb4fa><bar> <total>%</fc>"] 10
+      , Run Network "enp3s0" ["-S", "True", "-t", "eth: <fc=#4eb4fa><rx></fc>/<fc=#4eb4fa><tx></fc>"] 10
+      , Run Memory ["-t","mem: <fc=#4eb4fa><usedbar> <usedratio>%</fc>"] 10
+      , Run Date "date: <fc=#4eb4fa>%a %d %b %Y %H:%M:%S </fc>" "date" 10
+      , Run StdinReader
+      ]
+  , sepChar     = "%"
+  , alignSep    = "}{"
+  , template    = "  %StdinReader% | %cpu% | %memory% | %enp3s0%  }{%date%  "
+  }