Add a command alias for install command

[Zheaoli]

Many people will get a typo when using the pip install command such as pip isntall. so npm use a command alias to help people use the package manager correctly.

So is there any chance to add an alias? I can make a PR for this

[McSinyx]

This has already been worked on in GH-4193 and rejected because actions performed by pip could not be easily undone. I'm not so sure about the current state of pip however.

BTW if alias is the goal, is there and issue with shell alias? Edit: apparently it wouldn't be possible for most shells, unless a function is to be defined. However, I see no reason that pip cannot have just suggestion (but auto-correction) if mistyped subcommands. The hug is also an option for you though @Zheaoli.

[pradyunsg]

Bundling this with #8130 and closing this issue for keeping one tracking issue for all kinds of alias requests.

Thanks for filing this issue @Zheaoli! ^>^