feat: add go-getter plugin

[ryodocx]

Summary

• I want to add hashicorp 'go-getter' plugin for the asdf-vm
• go-getter can download things from a URL using a variety of protocols
• go-getter is used by Terraform, Helmfile and so on (as library)

repositories:

• go-getter: https://github.com/hashicorp/go-getter (not mine)
• asdf-plugin: https://github.com/ryodocx/asdf-go-getter

Checklist

• CI tests are green. If you are using GitHub, you might want to use the plugin_test action from asdf-actions
• asdf-plugins CI sanity checks are green on your PullRequest. Test locally with:

./test_plugin.sh --file plugins/<PLUGIN_FILE>

[jthegedus]

lgtm, thanks