Replace `sassc` with `dart-sass`

[davidjharder]

Old package sassc (Wrapper around libsass to compile CSS stylesheet) is archived at source, and should be replaced with dart-sass, which we do not package yet.

https://github.com/sass/sassc
https://sass-lang.com/dart-sass
https://github.com/sass/dart-sass

[davidjharder]

Existing package astroid uses libsass

[EbonJaeger]

Budgie Desktop also uses sassc. https://github.com/BuddiesOfBudgie/budgie-desktop/blob/v10.9.x/src/theme/meson.build#L4-L10

Nevermind.

[davidjharder]

Noting this so we don't forget, Budgie uses sasscs, but should be able to swap for dart-sass no problem

Actually, tons of packages use sassc. I was searching incorrectly