`jsr add` command should be able to install packages globally with `-g` or `--global` CLI flag

[arafathusayn]

What is the issue?

Currently these commands fail:

• npx jsr add -g <pkg>
• bunx jsr add -g <pkg>
• jsr add -g <pkg>

Why do we need it?

Some CLI "bin" packages need to be used installed globally. jsr CLI program itself should be installed globally via -g or --global flag.

Similar issue for deno add -g posted here: jsr-io/jsr#213