Add the deprecation-handling Sass options

[Amoifr]

Closes #89.

@stof spotted that the supported Sass options were missing the deprecation-related ones, and suspected #67 (repeated options) would need solving first. Good news: that part is already done — #37 taught SassBuilder to expand array values into repeated flags, which load_path already relies on. So this is just wiring up what's missing:

Config	Sass flag
verbose	--verbose	boolean
fatal_deprecation	--fatal-deprecation	repeatable
future_deprecation	--future-deprecation	repeatable
silence_deprecation	--silence-deprecation	repeatable

symfonycasts_sass:
    sass_options:
        fatal_deprecation: ['import']
        silence_deprecation: ['color-functions']

One caveat worth flagging: --silence-deprecation only exists since Dart Sass 1.74.0, while the binary this bundle downloads is pinned to 1.69.7. The other three work fine on the pinned binary (--future-deprecation works there even though sass --help doesn't advertise it — verified 🕵️). Every option defaults to null and is only emitted when set, so nothing changes for existing users; the docs note the version requirement.

Tests cover both the CLI flag expansion and a functional build: opting into the import deprecation early warns, and marking it fatal turns it into a build error. I also fixed the $sassOptions docblocks, which still claimed bool|string while load_path has been passing arrays since #37.

Thanks for the bundle! 🙏