docs: add front-end/web-components.md

[bennypowers]

This is an initial draft PR for web components guidance

Intended Audience:

• for customers internal and external rather than product teams
• for upstream rather than downstream
• for devs shipping products more than for devs writing libraries
• developers who are:
  • thinking of using wc as part of their fe stack
  • adding third party wcs to an existing project

[bennypowers]

This is an initial draft. all the bullet points will be expanded. We should add examples of usage at red hat, including both SPA and MPA cases

[lholmquist]

closing and using this one instead #13