RFC: `wakatime-find-binary` improvement

[pataquets]

I need to look for Wakatime's cli binary in ~/.local/bin. I'm aware I can manually configure it via wakatime-cli-path (my current workaround), but I was expecting it to work out of the box, as it's a common dir.

As per XDG Base Directory Specification, ~/.local/bin may contain user binaries. Also, ~/bin is also a common binary location (at least in Ubuntu's default .profile: filesystem - What's the purpose of $HOME/bin directory? - Ask Ubuntu)

Checking the code, neither of the above paths is checked. At first I thought on adding them and sending a PR. On second thought, I wonder why is not executable-find being used. Maybe some function's built-in behavior is not desired.

Before going further, some feedback would be appreciated.