Have protection against modifying things off screen

[pokey]

If a command, eg "chuck" is about to delete something you can't see, it should either fail or warn. Could have a setting to turn this one off if you like to live dangerously 😈

This protection would be important to have before we support #44

Fwiw this support could prob be implemented by a separate extension that Cursorless could then be a client of if it wanted to do something special

Here's some code to get us started. Was originally in extension.ts, but removed as part of #1035 as it is still just unused draft code:

  function checkForEditsOutsideViewport(
    event: vscode.TextDocumentChangeEvent
  ) {
    // TODO: Only activate this code during the course of a cursorless action
    // Can register pre/post command hooks the way we do with test case recorder
    // TODO: Move this thing to a graph component
    // TODO: Need to move command executor and test case recorder to graph
    // component while we're doing this stuff so it's easier to register the
    // hooks
    // TODO: Should run this code even if document is not in a visible editor
    // as long as we are during the course of a cursorless command.
    const editor = vscode.window.activeTextEditor;

    if (
      editor == null ||
      editor.document !== event.document ||
      event.reason === vscode.TextDocumentChangeReason.Undo ||
      event.reason === vscode.TextDocumentChangeReason.Redo
    ) {
      return;
    }

    const ranges = event.contentChanges
      .filter(
        (contentChange) =>
          !editor.visibleRanges.some(
            (visibleRange) =>
              contentChange.range.intersection(visibleRange) != null
          )
      )
      .map(({ range }) => range);

    if (ranges.length > 0) {
      ranges.sort((a, b) => a.start.line - b.start.line);
      const linesText = ranges
        .map((range) => `${range.start.line + 1}-${range.end.line + 1}`)
        .join(", ");
      vscode.window.showWarningMessage(
        `Modification outside of viewport at lines: ${linesText}`
      );
    }
  }

  vscode.workspace.onDidChangeTextDocument(checkForEditsOutsideViewport)