Improve vscode api get configuration

[AndreasArvidsson]

I have on purpose not migrated all references to vscode.workspace.getConfiguration because we might need to have a discussion if this is a preferable implementation first.

Checklist

• [-] I have added tests
• [-] I have updated the docs and cheatsheet
• [-] I have not broken the cheatsheet

[pokey]

not sure I'm in love with having something on vscodeApi that doesn't exactly mirror vscode api, as that's kind of what that object is for. I don't feel super strongly tho, so maybe let's discuss. We could maybe put it somewhere else