[Discussion] Special Use Cases of Shell Command Execution
@fox0430

I found the following two use cases of the `:!` command being pretty common in my development workflow:
- `:!echo` to see the recent terminal output, for example from a `grep` command for lines to edit
- `:!man <something>` to view a certain manual page, especially for C standard library functions

Both can be made easily into dedicated commands on their own as they are special cases of the regular command execution.  The first one is simply `shellCommand` without line 1085 (https://github.com/fox0430/moe/blob/develop/src/moepkg/exmode.nim#L1085) and could be named `bg`, for example, as it is the opposite action to the UNIX command `fg`.  Although Moe explicitly supports `Ctrl + Z` out of the box, a dedicated internal command might avoid forgetting about a paused Moe instance in the background.

The second one is another special case of `shellCommand` without the lines 1086 and 1087 (https://github.com/fox0430/moe/blob/develop/src/moepkg/exmode.nim#L1086; https://github.com/fox0430/moe/blob/develop/src/moepkg/exmode.nim#L1087) as the editor perspective would be restored automatically when `man` returns.  The command could be named `man` and take the arguments for `man` as parameters.  As it is already officially recommended to run Moe in a Linux environment, the presence of the `man` executable could be considered a sane assumption.

I would like to discuss whether it would be useful to give those two use cases commands on their own.