Add default theme and update screenshots (#160)

* Create sphaira_theme.ini

* Tweak colors and add default

* Add updated screenshots

assets/romfs/themes/default_theme.ini

@@ -0,0 +1,30 @@
+[meta]
+name=Default
+author=ninstar
+version=1.0.0
+inherit=romfs:/themes/base_black_theme.ini
+
+[theme]
+background = 0x111f28
+grid = 0x122430
+popup = 0x143144
+error = 0xfa3a5d
+
+line = 0x335e77
+line_separator = 0x163951
+
+text = 0xfbfbfb
+text_info = 0xbed0d6
+text_selected = 0x32ffcf
+selected_background = 0x143144
+
+sidebar = 0x071013ef
+
+scrollbar = 0x32ffcf
+scrollbar_background = ; hide the background
+
+progressbar = 0x32ffcf
+progressbar_background = 0x0B1519
+
+highlight_1 = 0x69ff8f
+highlight_2 = 0x5cbeff