Install wakatime-cli binary if missing

[gwennlbh]

Client plugins should install wakatime-cli themselves, see
https://wakatime.com/help/creating-plugin#plugin-init:wakatime-cli

[gwennlbh]

Hi! Just checking in, have you had the time to look at this? If you don't thats fine, ill release a first version of zed wakatime without this merged in ;)

[mrnossiom]

Hi ewen,

I have read Wakatime guidelines for plugins. This was more of a design decision than just straight not implementing it. I personally prefer to manage myself upgrades through declarative configuration.

This said, I am more than open to dicussion. I see how this could refrain users. I see two solutions:

• Update check and installation is instead implemented at the editor plugin level (e.g. in https://github.com/ewen-lbh/zed-wakatime).
• It is possible to integrate this at the LSP level with a flag (either CLI flag, non-standard key in the wakatime config, cargo feature).

Concerning the PR, a few comments:

• You should take into account the $WAKATIME_HOME env var. Wakatime is not always at ~/.wakatime.
• I think it would be cleaner to move installation and update check code to its own module.

Bonne journée