[clangd] Update dev dependencies of clangd-vscode

Summary:
The version bumps are a result of running `npm audit`, which found
3 security issues in previous versions of our dependencies.

Also add 'package-lock.json' to the repo, it's a common practice to
check in those files into the repository to get consistent versions of
dependencies when running on different machines.

Reviewers: hokein

Reviewed By: hokein

Subscribers: dschuff, ioeric, MaskRay, jkorous, arphaman, kadircet, cfe-commits

Tags: #clang

Differential Revision: https://reviews.llvm.org/D57814

llvm-svn: 353296