Add basic action-based editor, minorly improved from vello_editor. #340

Job	Run time
cargo check (msrv) (windows-latest)	41s
cargo check (msrv) (macos-latest)	53s
cargo clippy (windows-latest)	24s
cargo clippy (android) (armv7-linux-androideabi)	1m 42s
cargo check (msrv) (android) (armv7-linux-androideabi)	44s
cargo check (msrv) (ubuntu-latest)	37s
cargo clippy (macos-latest)	30s
cargo clippy (android) (aarch64-linux-android)	1m 47s
cargo check (msrv) (android) (aarch64-linux-android)	49s
cargo clippy (ubuntu-latest)	23s
cargo check (msrv) (android) (x86_64-linux-android)	49s
cargo clippy (android) (x86_64-linux-android)	1m 41s
cargo doc (windows-latest)	1m 22s
cargo doc (macos-latest)	28s
cargo fmt	24s
typos	3s
cargo doc (ubuntu-latest)	20s
cargo test (windows-latest)	1m 26s
cargo test (macos-latest)	32s
cargo test (ubuntu-latest)	25s
	16m 0s

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