Add the subcommand "bflat run"

[NetHunterZero]

I noticed in the README file that this is a Go-inspired tool. In the go cli, the commonly used commands are not only "go build" but also "go run", which can operate on single files. Therefore, whether to consider adding the "bflat run" subcommand to directly run C# source files, which can reduce certain build steps

[CypherPotato]

Already talked about it here.