URLSearchParams is missing "size" property

[shadow-identity]

Describe the bug
URLSearchParams should have its size property which indicates the total number of search parameter entries. However, happy-dom implementation always returns undefined when trying to access it.

To Reproduce
Steps to reproduce the behavior:

1. In node environment, for example in vitest, add this code:

   const searchParams = new URLSearchParams()
   console.log(searchParams.size)
   searchParams.append('foo', 'bar')
   console.log(searchParams.size)

2. Run and check the console output

Expected behavior
Console should return

0
1

But it returns

undefined
undefined

Device:

• OS: 14.4.1 (23E224)
• Node
• v18.14.0