helper-fsm package lists incorrect (?) license property

[dbjorge]

The @webassemblyjs/helper-fsm package.json lists "license": "ISC", but I suspect it's probably intended to be MIT:

• It doesn't include its own LICENSE file listing out the ISC license, which suggests the root-level MIT LICENSE file is intended to apply
• ISC is the default value of npm init
• Almost all other packages in the repo use MIT

It would be nice to update the license property, or if it actually is intended to be ISC, to add in a package-specific LICENSE file