Homepage button configuration

[EliTheGingerCat]

Adds the ability to add buttons to the default homepage via moonwave.toml.

[[home.buttons]]
text = "Download"
url = "https://github.com/evaera/moonwave/releases/download/v1.3.0/moonwave-extractor-v1.3.0-linux.zip"

Adding any buttons will remove the default "Get Started", so the equivalent TOML code for it is included on the website.

I was not sure how to properly add a margin between homepage buttons so I just used an inline style.

Closes #105

[YetAnotherClown]

Docusaurus provides many different styling options for buttons, it might be nice to expose these in the config file as well. You can find information about styling buttons on the Infima Website.

We could either just let the user set a className field on the button in the config file to do this, or we could introduce other fields for each way to style the button. What do you think?

[EliTheGingerCat]

I feel like the website does not explain enough how to use the different style options. The problem is:

1. Adding conflicting classes on the same button (such as active + disabled) would add more confusion.
2. Adding a separate button for each mutually exclusive class seems a bit much.

Perhaps people will just figure it out. I think it follows common sense. And they can always use the className field.