Clarify what events/traces/metrics are collected by default

[baywet]

Hi 👋 We're exploring this package to instrumentalize our vscode extension.

One thing that's not clear from the documentation/readme is what is collected by default. If the documentation tells us which properties are added to "manually" logged events, it doesn't tell us much else.

It'd be good to answer questions like:

• does it collect extension errors/crashes by default, or does the application developer need some kind of global try/catch/log?
• does it collect events automatically on command execution? Metrics about the command duration/number of times it was called?
• does it start/stop a session when the extension gets activated/deactivated?
• does it collect anything about users cohorts?
• does it collect any metrics on how much time users spend on the UI surfaces of the extension?

[lramos15]

Yeah the documentation can definitely be improved here. All this module provides is leveraging the VS Code API in both web and node environments using Microsoft telemetry systems such as App Insights and 1DS. It's goal is to be an easy starting point to add whatever events an extension feels comfortable with from a privacy perspective while respecting all the requirements we ask of VS Code Extension developers.

The only things that are collected for you are uncaught exceptions (exceptions, not crashes) and some common properties we find can be helpful https://github.com/microsoft/vscode/blob/cd1af5b0601470fbe9d58abe861485c9fdceee3b/src/vs/workbench/api/common/extHostTelemetry.ts#L98-L124