Broken links in the npm package documentation

[okoethibm]

The npm package documentation https://www.npmjs.com/package/@jupyterlab/services/v/6.3.2 has several broken links, which makes it hard to find how the API is actually used from javascript / nodejs

• the "REST API docs" link goes to
  http://petstore.swagger.io/?url=https://raw.githubusercontent.com/jupyter/notebook/master/notebook/services/api/api.yaml
  where the actual swagger at https://raw.githubusercontent.com/jupyter/notebook/master/notebook/services/api/api.yaml cannot be found

• the "Usage Examples" have broken links like
  https://github.com/jupyterlab/jupyterlab/blob/HEAD/examples/browser/src/comm.ts
  I suppose the correct link would be
  https://github.com/jupyterlab/jupyterlab/blob/master/packages/services/examples/browser/src/comm.ts
  same for the other examples

• the "architecture diagram" link at the bottom of the page is broken
  https://raw.githubusercontent.com/jupyterlab/jupyterlab/HEAD/architecture.png

• the "API docs" link at the top works but goes to the overall jupyterlab documentation source. It would be more helpful to lead to the API docs for the "services" module that is actually represented in the npm package, i.e.
  http://jupyterlab.github.io/jupyterlab/modules/_services_src_index_.html
  or maybe better
  https://jupyterlab.readthedocs.io/en/latest/api/modules/services.html

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[JasonWeill]

Thank you! NPM uses links from README.md in this package, so the fix should go into that file as well.