Activation event for a particular folder opened

<!-- ⚠️⚠️ Do Not Delete This! feature_request_template ⚠️⚠️ --> <!-- Please read our Rules of Conduct: https://opensource.microsoft.com/codeofconduct/ --> <!-- Please search existing issues to avoid creating duplicates. --> <!-- Describe the feature you'd like. --> Over in GistPad, they support "Wiki's": https://github.com/lostintangent/gistpad#wikis which provides an enlightened experience when: * The folder is named `foo-wiki` * The folder contains a `gistpad.json` or a `foam.json` The latter is easily covered by `workspaceContains` activation event but the former isn't possible I think. If the extension wants this feature, then it has to use `onStartupFinished` to activate which means this extension always activates even when you're not using Gists or Wikis. Perhaps we should explore adding another activation event called `workspaceName:*-wiki` or make `workspaceContains` also look at the folder name.