Rust

Add `Line::fill_alpha` #103

Job	Run time
android	26s
Check wasm32 + wasm-bindgen	2m 19s
cargo-deny aarch64-apple-darwin	46s
Format + check + test	5m 55s
Check Windows	2m 9s
cargo-deny aarch64-linux-android	40s
cargo-deny i686-pc-windows-gnu	41s
cargo-deny i686-pc-windows-msvc	37s
cargo-deny i686-unknown-linux-gnu	39s
cargo-deny wasm32-unknown-unknown	36s
cargo-deny x86_64-apple-darwin	35s
cargo-deny x86_64-pc-windows-gnu	36s
cargo-deny x86_64-pc-windows-msvc	37s
cargo-deny x86_64-unknown-linux-gnu	40s
cargo-deny x86_64-unknown-linux-musl	35s
cargo-deny x86_64-unknown-redox	37s
	18m 28s

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