Change div to span

Changes the mushroom counter to a span.
Span is the preferred element for inline-items, I think.
Add rudimentary CSS

Fixes #2.
Adds some simple stylesheets to make the game look nicer.
Create basic file structure

Fixes #4.
Splits the HTML, CSS and JavaScript into separate files.
Store mushrooms in global variable

The number of mushrooms are now stored in a variable instead of inside
a HTML element.
Add simple auto-clicker functionality

The player can now create phantom hands that auto-click every second.
Run initializer function on page load

Adds a function called "initGame" that is run on page load, intended to
update game-related HTML elements with relevant data.
Add price to clicker

Auto clicker now costs 10 mushrooms
Limit "auto-clicks" per second

Fixes #3.
The auto-clickers now stop auto-clicking after a number of auto-clicks per
second. When this limit is hit, the number of mushrooms per auto-click is
increased instead.