Consider adding support for "deno add -g"

[bartlomieju]

$ deno add -g jsr
error: unexpected argument '-g' found

  tip: to pass '-g' as a value, use '-- -g'

Usage: deno add [OPTIONS] <packages>...

For more information, try '--help'.

-g would pull a package and make a global alias for it. Somewhat related to #22754.

Originally reported by @arafathusayn in jsr-io/jsr#213

[kt3k]

Does this only work for CLI tool type packages? What happens if we call this with library type package?