Fix potential misalignment of text menu

Any style overrides from the mpv.conf shouldn't matter because of the
\rDefault, but apparently it's still possible to break alignment somehow,
so simply set an alignment to what we need.

ref. #40

quality-menu.lua

@@ -748,7 +748,7 @@ local function text_menu_open(formats, active_format, menu_type)
         local clip_top = math.floor(margin_top * height + 0.5)
         local clip_bottom = math.floor((1 - margin_bottom) * height + 0.5)
         local clipping_coordinates = '0,' .. clip_top .. ',' .. width .. ',' .. clip_bottom
-        ass:append('{\\rDefault\\q2\\clip(' .. clipping_coordinates .. ')}' .. opts.style_ass_tags)
+        ass:append('{\\rDefault\\an7\\q2\\clip(' .. clipping_coordinates .. ')}' .. opts.style_ass_tags)
 
         if #formats > 0 then
             for i, format in ipairs(formats) do