docs: improve documentation about disconnection

There are two cases (and not one) where the client will not try to
reconnect automatically.

Related: socketio/socket.io-client#1443

source/docs/v3/client-api.md

@@ -493,7 +493,9 @@ Reason | Description
 `transport close` | The connection was closed (example: the user has lost connection, or the network was changed from WiFi to 4G)
 `transport error` | The connection has encountered an error (example: the server was killed during a HTTP long-polling cycle)
 
-In all cases but the first (disconnection by the server), the client will wait for a small random delay and then reconnect.
+In the first two cases (explicit disconnection), the client will not try to reconnect and you need to manually call `socket.connect()`.
+
+In all other cases, the client will wait for a small [random delay](/docs/v3/client-initialization/#reconnectionDelay) and then try to reconnect:
 
 ```js
 socket.on('disconnect', (reason) => {

source/docs/v3/client-socket-instance.md

@@ -149,6 +149,20 @@ Reason | Description
 `transport close` | The connection was closed (example: the user has lost connection, or the network was changed from WiFi to 4G)
 `transport error` | The connection has encountered an error (example: the server was killed during a HTTP long-polling cycle)
 
+In the first two cases (explicit disconnection), the client will not try to reconnect and you need to manually call `socket.connect()`.
+
+In all other cases, the client will wait for a small [random delay](/docs/v3/client-initialization/#reconnectionDelay) and then try to reconnect:
+
+```js
+socket.on("disconnect", (reason) => {
+  if (reason === "io server disconnect") {
+    // the disconnection was initiated by the server, you need to reconnect manually
+    socket.connect();
+  }
+  // else the socket will automatically try to reconnect
+});
+```
+
 Note: those events, along with `disconnecting`, `newListener` and `removeListener`, are special events that shouldn't be used in your application:
 
 ```js

source/docs/v3/server-api.md

@@ -799,8 +799,9 @@ Possible reasons:
 
 Reason | Description
 ------ | -----------
-`io server disconnect` | The socket was forcefully disconnected with [socket.disconnect()](/docs/v3/server-api/#socket-disconnect-close)
-`io client disconnect` | The client has manually disconnected the socket using [socket.disconnect()](/docs/v3/client-api/#socket-disconnect)
+`server namespace disconnect` | The socket was forcefully disconnected with [socket.disconnect()](/docs/v3/server-api/#socket-disconnect-close)
+`client namespace disconnect` | The client has manually disconnected the socket using [socket.disconnect()](/docs/v3/client-api/#socket-disconnect)
+`server shutting down` | The server is, well, shutting down
 `ping timeout` | The client did not respond in the `pingTimeout` range
 `transport close` | The connection was closed (example: the user has lost connection, or the network was changed from WiFi to 4G)
 `transport error` | The connection has encountered an error