fix(openingh-nvim): more precise lazy loading with "cmd" and "keys"

[RayJameson]

📑 Description

Use keys and cmd for lazy loading openingph-nvim instead of event
I made the description of the keys generic on purpose because the plugin author states that it supports not only Github but also other git hosting sites. Also, this plugin has a nice notification message if you try to use it not inside a git repository so I don't see a problem with using cmd and keys

[github-actions]

Review Checklist

Does this PR follow the [Contribution Guidelines](development guidelines)? Following is a partial checklist:

Proper conventional commit scoping:

• If you are adding a new plugin, the scope would be the name of the category it is being added into. ex. feat(utility): added noice.nvim plugin

• If you are modifying a pre-existing plugin or pack, the scope would be the name of the plugin folder. ex. fix(noice-nvim): fix LSP handler error

• Pull request title has the appropriate conventional commit type and scope where the scope is the name of the pre-existing directory in the project as described above

• README is properly formatted and uses fenced in links with <url> unless they are inside a [title](url)

• Proper usage of opts table rather than setting things up with the config function.