Improve the track page layout

[mgumz]

This PR improves the track page layout in various aspects:

• An additional column to carry the play/pause state is added.

• The track number column is right aligned. Its maximum width is calculated based upon the number of tracks (before it was hardcoded to '4', assuming rightfully so 9999 tracks is pretty large). The track number column title '#' is now visually stable ontop of the actual track number.

[AdyStudios]

What theme is that btw?

[mgumz]

What theme is that btw?

a slight variation of "dracula":

name = "dracula.mathias"
[themes.palette]
background = "#1e1f29"
foreground = "#f8f8f2"
black = "#000000"
red = "#ff5555"
green = "#50fa7b"
yellow = "#f1fa8c"
blue = "#bd93f9"
magenta = "#ffa000"  # section-marker
cyan = "#8be9fd"
white = "#bbbbbb"
bright_black = "#555555"
bright_red = "#ff5555"
bright_green = "#50fa7b"
bright_yellow = "#f1fa8c"
bright_blue = "#bd93f9"
bright_magenta = "#ff79c6"
bright_cyan = "#8be9fd"
bright_white = "#ffffff"

[AdyStudios]

Awesome, thanks!