Install leaves support files to current directory

[ivuorinen]

Describe the bug

The install script should run git clone to a temporary directory that gets cleaned after install process. Now the install process leaves repo files to the directory where the installation was performed.

Noticed this after installing and the following files were caught in my $HOME/.dotfiles/scripts/ folder. Here's the git status:

Untracked files:
  (use "git add <file>..." to include in what will be committed)
        .github/
        README.md
        img/
        lib/
        set-env.fish
        set-env.zsh

Steps to reproduce

Add this plugin and run install.

Expected behavior

The install process shouldn't leave any repo related support files after installation.

Additional context

Please see these other plugins install scripts for inspiration:

• https://github.com/asdf-community/asdf-direnv/blob/master/bin/install
• https://github.com/asdf-community/asdf-golang/blob/master/bin/install#L16-L26
• https://github.com/asdf-community/asdf-hashicorp/blob/master/bin/install#L21-L24