Keep CodeRoad webview on top

[ShMcK]

There are times where the webview falls behind other editor views.

Solutions for this include:

1. waiting for VSCode to allow webviews in the side panel
2. listening to editor changes and triggering the webview to jump back on top. This may be annnoying
3. determining times when CodeRoad triggers the webview into the background and triggering a fix for these. It's really only an issue when the webview hides its self due to loaded files in the workspace.

I'm thinking 3 may be a good strategy. 1 can be considered in the future.

[ShMcK]

This seems to be possible in an upcoming version of VSCode, where webviews can be put into the main side panel (eg. where the git, extensions, etc live). The PR was merged last week.

[ShMcK]

Now available as a "Proposed API". https://code.visualstudio.com/updates/v1_49#_webview-views