Remove some dependencies

[Leleat]

Unfortuntely, currently I use quite a few deps for this small CLI. Some of the deps could probably be easily removed. Looking through the deps the following could be considered:

• url
  • After a quick search, I only seem to use byte_serialize to encode the gitlab path, which could be done manually since I only need to replace /, which could be done manually safely since project and usernames can't contain / and other characters don't encoding: https://docs.gitlab.com/user/reserved_names/#rules-for-usernames-project-and-group-names-and-slugs
• dialoguer
  • I use its prompt and editor feature. Both probably shouldn't be hard to implement myself.
• confy
  • Loads/saves config files from/to common locations, e.g. XDG config directory. This may be more complicated since I need to consider cross-platform support, fallbacks, etc.
• open
  • Opens links with the user's default browser. On linux there is xdg-open but I have no clue about cross-platform support...