Performance improvement

**Is your feature request related to a problem? Please describe.**
We are seeing very slow response times using the library to write to a NUS serial service tx characteristic. For example, using python with the bleak BLE library we are seeing around 7-10ms response times. For the same request using angular-web-bluetooth library we are seeing on average 300 - 400ms response times. Our application requires many requests to load data from our devices so we would love to see similar performance to the python script.

**Describe the solution you'd like**
An improvement in the amount of time for the write subscription to return. Here is an example of a request we are making:
this.bluetooth.writeValue$(this.feritConnection.rx, slice)
.subscribe(() => { console.log("This on average takes around 300 - 400ms to return");};

**Additional context**
Cleaner screenshot of code we are using to write to the NUS serial service tx characteristic:


Definition of the NUS serial service:

Start at the implementation of writeValue$ and trace the Web Bluetooth write path used for the NUS serial service tx characteristic. Measure the latency of the shown writeValue$ request, identify where the delay occurs, and verify that the callback returns substantially faster without breaking the write flow.

Written by the indexing model from the issue text.