Investigate running the Docker extension in web

[bwateratmsft]

Many extensions are being converted to run in the browser; I'd like to investigate if the Docker extension (the language services and maybe scaffolding in particular) can be made to work in the browser as well. Dockerfile and compose file editing comprise the vast majority of the extension usage, so having support in browser makes a lot of sense in my mind.

[dbreshears]

Keeping open as someday we may enable the language services in the browser