[lldb-vscode] Make it possible to run vsce package

Summary:
Running `vsce package` to package lldb-vscode as an installable .vsix file errors with:

```
ERROR  Invalid publisher name 'llvm.org'. Expected the identifier of a publisher, not its human-friendly name.
```

This patch fixes the publisher name and bumps a required dependency so that `vsce package` succeeds.

Reviewers: clayborg

Reviewed By: clayborg

Tags: #lldb

Differential Revision: https://reviews.llvm.org/D80569