Add basic action-based editor, minorly improved from vello_editor. #342

Job	Run time
cargo clippy (windows-latest)	2m 3s
cargo clippy (android) (armv7-linux-androideabi)	1m 44s
cargo clippy (macos-latest)	51s
cargo clippy (android) (aarch64-linux-android)	1m 41s
cargo check (msrv) (windows-latest)	54s
cargo clippy (ubuntu-latest)	48s
cargo check (msrv) (android) (armv7-linux-androideabi)	47s
cargo check (msrv) (macos-latest)	1m 12s
cargo clippy (android) (x86_64-linux-android)	1m 39s
cargo check (msrv) (android) (aarch64-linux-android)	51s
cargo check (msrv) (ubuntu-latest)	52s
cargo check (msrv) (android) (x86_64-linux-android)	46s
cargo doc (windows-latest)	1m 22s
cargo fmt	23s
cargo test (windows-latest)	1m 28s
cargo doc (macos-latest)	28s
typos	5s
cargo test (macos-latest)	27s
cargo doc (ubuntu-latest)	19s
cargo test (ubuntu-latest)	25s
	19m 5s

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