Add some extra default color schemes

[AObuchow]

Since I intend to allow users to save & load color schemes, it makes sense to include some extra default color schemes. I'm making this bug to track color schemes that I like and might want to include.

[AObuchow]

ColorScheme {
    --background-color: #1F2531;
    --base-color: #252C3B;
    --accent-color: #D70000;
}

Based off of the Godot Editor's color scheme.

[AObuchow]

ColorScheme {
    --background-color: #0E1014;
    --base-color: #171C26;
    --accent-color: #C4A000;
}

Similar to above, just darker and with yellow accent

[AObuchow]

ColorScheme {
    --background-color: #0C141B;
    --base-color: #101C27;
    --accent-color: #D70072;
}