install script should automatically add the install directory to `PATH`

[DetachHead]

What is the problem this feature will solve?

when i install bun i have to manually figure out which .bashrc file to add these lines to:

What is the feature you are proposing to solve the problem?

the script should do it for me

What alternatives have you considered?

No response

[JL102]

I suppose a dirty solution would be to:

1. First test to see if the install dir happens to already be on PATH
2. If not, then check for common rc files in the home dir (.bashrc, .cshrc, etc.), and add it to whichever of those files already exist.

But it should ask the user before automatically adding it, IMO.