API changes:
- `Key.isPublic()` has been removed, since it was redundant and it would
introduce TypeScript issues. Call `!Key.isPrivate()` instead.
TypeScript changes:
- the `openpgp.readKey(s)` functions are now declared as returning a `Key`
instead of a `PublicKey`. This is just a readability improvement to make it
clearer that the result could also be a `PrivateKey`.
- All `Key` methods that return a key object now have the narrowest possible
return type.
- The `Key.isPrivate()` method can now be used for type inference, allowing the
compiler to distinguish between `PrivateKey` and `PublicKey`.
Calling `key.isPrivate()` is the recommended way of distinguishing between a
`PrivateKey` and `PublicKey` at runtime, over using `key instanceof ...`, since
the latter depends on the specifics of the `Key` class hierarchy.
d238a023c1