feat(ft): add xonsh support (#363)

Doc: https://xon.sh/tutorial.html

Author: FraserLee

lua/Comment/ft.lua

@@ -150,8 +150,9 @@ local L = setmetatable({
     vim = { M.vim },
     vifm = { M.vim },
     vue = { M.html, M.html },
-    xml = { M.html, M.html },
     xdefaults = { '!%s' },
+    xml = { M.html, M.html },
+    xonsh = { M.hash }, -- Xonsh doesn't have block comments
     yaml = { M.hash },
     yuck = { M.lisp_l },
     zig = { M.cxx_l }, -- Zig doesn't have block comments