[BridgeJS] @JSClass does not work on `public` or `package` types

[sliemeobn]

The macro adds a conformance to _JSBridgedClass, but generates initializer and jsObject field with internal access level.

Property 'jsObject' must be declared public because it matches a requirement in public protocol '_JSBridgedClass'
Initializer 'init(unsafelyWrapping:)' must be declared public because it matches a requirement in public protocol '_JSBridgedClass'

[kateinoigakukun]

Fixed in main branch #640