Web support

[isc-bsaviano]

This PR fixes #232 and fixes intersystems-community/vscode-objectscript#1491. I was able to get this extension to activate in the web, and almost all features work. However, there are two behavior differences that make this substantially less useful in the web:

1. When the extension attempts to make a REST request using just cookies or no auth and a 401 is returned, the browser hijacks this and presents its basic auth prompt instead of letting us supply the username and password.I can see if there's a way to remediate this behavior, maybe by stripping the WWW-Authenticate header from the response before the browser sees it. I doubt that will work though.
2. CORS restrictions mean that REST requests to servers with a different origin are rejected. I don't know if we can do anything about this on the extension side.

II still think this is good enough to meet our needs, but I wanted to be fully transparent about the limitations in case you can't try it out yourself.

[gjsjohnmurray]

Changes look good, and the dev VSIX is running fine on Desktop. I'm happy for it to be merged as is, despite the limitations you have described. It will be easier for me to test the behaviour in a browser once merged to master.