ensureRelay reconnect

[syusui-s]

The current implementation of ensureRelay connects to relays for the first time only. The second invocation of ensureRelay doesn't try to reconnect the relay even if it is disconnected.

This PR fixes that. It will try to connect if relay is disconnected.

Detail

The current implementation tries to send messages even if the connection is closed.
It causes the following error when I call pool.subscribeMany([failedRelay], ...):

Uncaught (in promise) Error: sending on closed connection

nostr-tools/pool.ts

Line 106 in a9acdad

let subscription = relay.subscribe(filters, {

If this PR is merged, the connection error exception will be raised in this try block and it will be handled correctly.

nostr-tools/pool.ts

Lines 97 to 104 in a9acdad

	try {
	relay = await this.ensureRelay(url, {
	connectionTimeout: params.maxWait ? Math.max(params.maxWait * 0.8, params.maxWait - 1000) : undefined,
	})
	} catch (err) {
	handleClose(i, (err as any)?.message || String(err))
	return
	}