Support canary builds

[Electroid]

Similar to bun upgrade --canary, brew install bun@canary should install from the last successful build on the main branch.

[Electroid]

It looks like Homebrew doesn't like when a version is "canary".

Expected to find class Bun@canary, but only found: BunATCanary

That's not possible to do in Ruby, since the class needs to be defined as:

class Bun@canary < Formula # invalid
end