feat(sorting): add sorting kinds of `pushed_at` and `stars` for themes.

[BeyondMagic]

Adds the following:

1. script to gather information from repositories using Github API, Gitlab API, Codeberg API, and cloning;
2. script will remove themes that are deleted online or it can't access, but will warn whoever is running it;
3. script written in Nushell for the sake of convenience;
4. script needs to run manually to update themes information (once a month is fine);

To-dos:

• [x] Concise documentation on how to run the script.
• [x] In documentation, add the field repository (for the script) when users try to add a new theme; users may use their theme's website in the link field.
• [x] Simple context menu to choose a sorting option, right now it's just toggling and it's annoying.

Preview:

---

Closes #274.