Broken references in Generic Sensor API

[dontcallmedom-bot]

While crawling Generic Sensor API, the following links to other specifications were detected as pointing to non-existing anchors:

• [ ] https://w3c.github.io/webdriver/#dfn-extension-command
• [ ] https://w3c.github.io/webdriver/#dfn-errors
• [ ] https://w3c.github.io/webdriver/#dfn-sessions
• [ ] https://w3c.github.io/webdriver/#handling-errors

_{This issue was detected and reported semi-automatically by Strudy based on data collected in webref.}

[anssiko]

I believe @rakuco will be addressing these and possibly also other WebDriver-related clarifications and fixes.

[rakuco]

I've got a fix here but can't get Bikeshed to find the WebDriver definitions I am referencing -- I've filed tabatkins/bikeshed#2416