Refactor ping packet handling in WebsocketTransport

[URVL]

Server-server connection ping error

• Changed PING_PACKET from a Buffer to an object for improved clarity.
• Updated the method call from this.write(PING_PACKET) to this.send(PING_PACKET) to reflect the new structure.

This change enhances the readability and maintainability of the code related to pinging in the WebSocket transport layer.

• [ +] tests and linter show no problems (npm t)
• [+ ] tests are added/updated for bug fixes and new features
• [+ ] code is properly formatted (npm run fix)
• [+ ] description of changes is added in CHANGELOG.md
• [ +] update .d.ts typings

[nechaido]

The issue is that when ping is send as a buffer - it is treated as a binary here
Here:
https://github.com/metarhia/metacom/blob/master/lib/server.js#L207

Which results in
https://github.com/metarhia/metacom/blob/master/lib/streams.js#L18

Trring to read 32 bytes from a 16byte buffer, this lead to server failure.

Alternative solution would be to use "{}" without the buffer and test to see if it works that way.

[tshemsedinov]

1. @URVL @nechaido If I remember rightly, Websockets has built-in ping mechanism, so we do not need this for WebsocketTransport, just for TCP/UDP
2. For other transports we can use string '{}', not buffer or empty object {}
3. It is strange, that chunkEncode/Decode works with ping packets, I think {} is a textual packet