worker: clarify API stability

Author: ShogunPanda

doc/api/worker_threads.md

@@ -67,13 +67,17 @@ specifically `argv` and `execArgv` options.
 added: REPLACEME
 -->
 
+> Stability: 1.1 - Active development
+
 * `target` {number} The target thread id.
 * `data` {any} Any arbitrary, cloneable JavaScript value.
 * Returns: {MessagePort}
 
 Establishes a connection to another worker thread in the same process, returning a
 `MessagePort` that can be used for the communication.
 
+The thread will be blocked while waiting for the port from the other thread.
+
 The target thread must have a connection listener setup via [`worker.setConnectionsListener()`][]
 otherwise the connection request will fail.
 
@@ -347,6 +351,8 @@ new Worker('process.env.SET_IN_WORKER = "foo"', { eval: true, env: SHARE_ENV })
 added: REPLACEME
 -->
 
+> Stability: 1.1 - Active development
+
 * `fn` {Function} A callback to be executed when [`worker.connect()`][] is called from another thread.
   The function will received the following arguments: