Make StyleProperty::FontStack more ergonomic. #357

Job	Run time
cargo clippy (windows-latest)	42s
cargo clippy (android) (armv7-linux-androideabi)	55s
cargo check (msrv) (android) (armv7-linux-androideabi)	1m 4s
cargo clippy (macos-latest)	41s
cargo clippy (android) (aarch64-linux-android)	53s
cargo check (msrv) (windows-latest)	3m 44s
cargo check (msrv) (android) (aarch64-linux-android)	1m 6s
cargo clippy (ubuntu-latest)	38s
cargo clippy (android) (x86_64-linux-android)	52s
cargo check (msrv) (android) (x86_64-linux-android)	1m 1s
cargo check (msrv) (macos-latest)	1m 18s
cargo check (msrv) (ubuntu-latest)	1m 12s
cargo fmt	24s
cargo doc (windows-latest)	3m 0s
cargo test (windows-latest)	4m 43s
cargo doc (macos-latest)	1m 1s
typos	4s
cargo test (macos-latest)	1m 48s
cargo doc (ubuntu-latest)	1m 11s
cargo test (ubuntu-latest)	1m 52s
	28m 9s

Provide feedback