Migrate to an organizational structure

**Is your feature request related to a problem? Please describe.**

We often get card requests from users that want to add new cards (i.e., #1563 and #1786). Currently, we have to decline these requests due to [GitHub's rate limits](https://docs.github.com/en/graphql/overview/resource-limitations) and maintainability concerns (see https://github.com/anuraghazra/github-readme-stats/issues/1563#issuecomment-1137509321).

**Describe the solution you'd like**

Splitting up our codebase to separate repositories under the [readme-stats](https://github.com/readme-stats) repository could solve this. This would allow users to implement their cards and transfer them to the organization for maintenance. I would therefore like to propose a structure like this:

- **Github-readme-stats:** (fetchers, stats, language, repo cards and core card generation functions)
- **gitlab-readme-stats:** (fetchers, stats, language, repo cards)
- **wakatime-readme-stats:** (fetcher, waketime card).
- **leetcode-readme-stats:** (fetcher, leetcode card).

I know this is a significant design change, but after #1633 is complete, we can move our card creation code to a separate npm package so users can use it to create their cards. An additional benefit of such a structure would be to include more maintainers since organizations allow for more precise permission management.