[feature] Split environment variable used for edits

[xPMo]

I prefer using VISUAL='vim --remote-wait-silent', so that editing files with $VISUAL happen in my existing session. However, rbw does not split environment variables to run commands, resulting in:

$ rbw edit DEMO
thread 'main' panicked at 'called `Result::unwrap()` on an `Err` value: Os { code: 2, kind: NotFound, message: "No such file or directory" }', src/edit.rs:44:10
note: run with `RUST_BACKTRACE=1` environment variable to display a backtrace

[doy]

fixed in 00e90e7