Because the keychain doesn't create keys, only accepts them, allow
importing the "self" key.

If the key already exists it will fail, and you still can't remove
or rename it.

Adds a type guard function to signal to tsc that an object
implements the PubSub interface.

Adds the ability to find configured services that possess a given
capability and interact with that service via rpc.

Starts with a configured PubSub service.

Read incoming ping messges in 32 byte chunks as per the spec and
echo them back to the sending peer.

If the remove fails to send us 32 bytes, reset the stream with a
`TimeoutError`.

ECDH over P-521 returns 66 bytes, i.e. 528 bits. Requesting 521 bits causes the last 7 bits of the derived value to be set to 0, which seems unintended (the Node.js version doesn't do this). So, request 66 * 8 bits instead.

Also, remove the superfluous `namedCurve` property in the algorithm identifier passed to `deriveBits` (it's only necessary when importing or generating keys).

- Add `Histogram`, `HistogramGroup`, `Summary`, `SummaryGroup` metric types
- Add `registerHistogram`, `registerHistogramGroup`, `registerSummary`, `registerSummaryGroup` methods to `Metrics` interface
- Add corresponding implementations to prometheus and simple metrics packages