Expand public configuration and allow for API keys

[danpastori]

Problem

As we integrate more social networks, such as subscribe on Youtube, we might need
to account for public facing API keys or username data.

Rationale

As we expand more buttons, and use Shr for more features, just allowing the user
to pass in the proper API keys/username data will be extremely helpful.

Solution

I'll expand the config to allow for more buttons to be added by handling API keys,
user names, or other config options.

Pros of Solution:

• Shr will allow for more buttons to be added.

Cons of Solution:

• Shr will handle more featurs, but is this something you want?

If you'd like to move forward, let me know and I'll submit a PR!

[sampotts]

Makes total sense to do this 👍