move to strict categories and create examples for them

[bnb]

per a discussion with @codebytere and extending a discussion with @joesepi, before we start sharing this repository more widely we should populate it with more examples.

some points that have come up:

• instead of allowing freeform categories, we should have more rigid categories that don't necessarily leave the option of creating categories up to contributors
  • in doing this, we should definitely have examples in the categories rather than having them be empty
  • we should probably work on the categories and figure out who'd be willing/able to add things to them

additionally, this will mean the README.md needs to be updated to effectively reflect limited categories

[bnb]

My thoughts on what categories should exist with examples:

• applications (electron, ionic, react native)
• cli (yargs, commander, inquirer, chalk(?))
• databases (mongodb, postgres)
• deployment (Docker, Terraform, AWS, GCP, IBM Cloud, Heroku, Netlify, Now)
• servers (express, fastify, restify, Hapi)
• ai/ml (tensorflow.js, others?)
• utilities (lodash, moment/luxon)

I'm sure I'm missing some?

[bnb]

This was implemented in #6 🥳