Add Nord theme (and lazy load vsc theme extensions)

Thanks @iljo-dp for finding the themes!

themes/alacritty/nord.toml

@@ -0,0 +1,47 @@
+[colors]
+[colors.primary]
+background = "#2e3440"
+foreground = "#d8dee9"
+dim_foreground = "#a5abb6"
+
+[colors.cursor]
+text = "#2e3440"
+cursor = "#d8dee9"
+
+[colors.vi_mode_cursor]
+text = "#2e3440"
+cursor = "#d8dee9"
+
+[colors.selection]
+text = "CellForeground"
+background = "#4c566a"
+
+[colors.normal]
+black = "#3b4252"
+red = "#bf616a"
+green = "#a3be8c"
+yellow = "#ebcb8b"
+blue = "#81a1c1"
+magenta = "#b48ead"
+cyan = "#88c0d0"
+white = "#e5e9f0"
+
+[colors.bright]
+black = "#4c566a"
+red = "#bf616a"
+green = "#a3be8c"
+yellow = "#ebcb8b"
+blue = "#81a1c1"
+magenta = "#b48ead"
+cyan = "#8fbcbb"
+white = "#eceff4"
+
+[colors.dim]
+black = "#373e4d"
+red = "#94545d"
+green = "#809575"
+yellow = "#b29e75"
+blue = "#68809a"
+magenta = "#8c738c"
+cyan = "#6d96a5"
+white = "#aeb3bb"