Read current code language from within visualizer

[zspitz]

Two uses:

• Default code language
• When copying the path to the expression for use in the Watch window (#13), it's important to format indexers correctly (this is independent of the currently selected formatter)

https://stackoverflow.com/q/55954016/111794

[zspitz]

For the default code language, this is a low priority, as it's only for the first time the visualizer is opened. After that, I think we want the settings to override the default.

For knowing in which language to produce the watch expression, that is a higher priority. It's currently possible to workaround this by changing the setting,