added custom-elements-ts in the libraries

[aelbore]

• add this library
• also can you also add this create-custom-elements boilerplate or starter?
  https://github.com/aelbore/create-custom-elements

[web-padawan]

Thanks for the PR! I think the library can be included here as a demonstration of using TS.

Regarding your request about the starter, I will consider adding a corresponding section but currently I'm not sure if we should promote this kind of projects.

Libraries are good in terms of how one could build something on top of the native Web Components specs, but starters are always opinionated and tend to promote certain stack which is not the primary goal of this project.

[web-padawan]

Merging your PR now, and submitted #38 to discuss the starters (boilerplates) thing more.