test: Updated toBeInTheDocument (#44)

The toBeInTheDocument was using the wrong selector like the README. Resetting it to check on the actual svg element.

Author: smacpherson64

src/__tests__/to-be-in-the-document.js

@@ -4,7 +4,7 @@ test('.toBeInTheDocument', () => {
     <svg data-testid="svg-element"></svg>`
 
   const htmlElement = document.querySelector('[data-testid="html-element"]')
-  const svgElement = document.querySelector('[data-testid="html-element"]')
+  const svgElement = document.querySelector('[data-testid="svg-element"]')
   const detachedElement = document.createElement('div')
   const fakeElement = {thisIsNot: 'an html element'}
   const undefinedElement = undefined