title: VSCode Extension : How can we use Monaco editor to edit in-memory Strings?
body: <p>I am building a Vscode/Theia extension, to contribute custom diagram-based editors. Within these editors, on certain events like node label-edit I need to provide input controls to end users where they can enter expressions based on our custom grammar definition. The purpose is to provide end-users a complete editing experience backed by LSP instead of a plain input textbox. My requirement is to have a reusable widget that will look similar to TextArea but with additional LSP support to assist the end-user in writing the expression.</p>
  <p>What I have done till now -</p>
  <ol>
  <li><p>vscode-extension for language support is created , language client &amp;
  server is getting initiated by this .</p>
  </li>
  <li><p>LSP features like content assist, error highlighting, etc. are
  working fine on a standalone file editor.</p>
  </li>
  <li><p>I am able to embed the Monaco editor in Diagram-based editor within
  HTML div, but none of the LSP features are working on it.</p>
  </li>
  </ol>
  <p>So how can we use Monaco editor to edit non-file resources like in-memory strings with all the LSP features enabled?</p>