Reformat README to be more readable

[Aquafina-water-bottle]

This PR reformats the README to simply do the following:

• Hide the sample requests/results with a details tag
• Move the action names from a list bullet point to a h4 title
• And some very minor stylistic changes, such as adding a line between the action categories to better separate them.

To see how the changes look in action, click here.

I personally find the documentation in the README difficult to read due to the amount of vertical scrolling I have to do, and it seems like it will only get worse as the API expands. Hiding the sample requests and results prevents a lot of extra scrolling, and allows the user to read the actual documentation behind the API easier. Additionally, moving the action names to a h4 title has the added benefit of being able to permalink to any specific action.

Some notes:

• These changes were inspired by how Yomichan's template helpers are already documented.
• I don't know if this will look good on the foosoft.net website (especially with the new line divisions between the action categories). It might be a good idea to see how the changes look there beforehand.

As with all stylistic changes, there are bound to be differing opinions, so I would love to hear any feedback!

[FooSoft]

Ooh! I like this. The markup probably won't look this good initially to start foosoft.net, but I have no problems styling it :)